3. CLIPS The arrow points to your clips tool bar. This is where you will drag and drop the video clips, images, and sound files that you want to include in your video. Note that these clips will not actually be in your movie until you drag and drop them into your video, like so:

 

When the clip appears highlighted in blue in the timeline toolbar, you know it will be part of the final movie you export. 

To edit the length of your video clips: (taken from iMovie Help)

Cropping video clips

Cropping allows you to edit a clip by keeping only the portion of video you like and removing the rest.

It's a good idea to crop your clips before dragging them out of the Clips pane and into your movie. However, you can also crop a clip after you've added it to your movie by selecting it in the clip viewer or timeline viewer.

To crop a clip:

1. Select the clip you want to crop by clicking it in the Clips pane, clip viewer, or timeline viewer.
2. Drag the playhead (A, shown above) to where you want your scene to begin.
3. Place your pointer (B, shown above) just below the playhead, and then drag to the right to include the footage you want to keep.

The gold portion of the scrubber bar (shown below) highlights the footage you've selected.

4. To precisely adjust where the selected footage begins and ends, click a crop marker (shown below) to select it, and then press the Left or Right Arrow key to move the crop marker one frame at a time. To move the marker in ten-frame increments, hold down the Shift key while pressing the arrow key.

Tip: You can see the duration of your selected footage in minutes:seconds:frames at the bottom edge of the iMovie window.

5. Choose Edit > Crop to keep the portion of video you've highlighted and remove the rest.

If you want to trim away only the beginning or end of a clip, drag the crop markers to highlight the portion you want to remove, and then choose Edit > Clear.

When cropping, keep in mind that iMovie HD only hides the footage you don't want to show and doesn't actually remove or delete it. If you trim away too much, you can always choose Edit > Undo to cancel your change, or extend the clip back to the desired length by dragging one of its edges in the timeline viewer. For more information, see "Fine-tuning where a clip begins and ends."

4.MEDIA The top bar is for film, picture, transition and title slides, and other visual elements of your movie, while the second two bars are for sound. Note that where you place sound clips on the timeline is directly connected to when they will play in the movie. To add preloaded audio clips, go to the media toolbar (two over from "clips") and click the audio button. Next, drag and drop the audio clip of your choice into the timeline bar, placing it at the point where you'd like it to occur in the movie. 

Note that you can record your own voice-over clip by clicking on the red record button next to the microphone decibel monitor bar (the one that progresses from black to red and sits below the "place at playhead" button and above the various toolbar buttons.)

There are several ways to edit the audio clip, including length and volume. (taken from iMovie Help):

Changing the length of an audio clip

You can trim the ends of audio clips to fit your video or to eliminate sound problems, such as hissing or static, at the beginning or end of an audio clip.

To change the length of an audio clip:

1. Click the Timeline Viewer button (shown above).
2. Select the audio clip in the timeline viewer.

IMPORTANT: You can't trim an audio clip if you're showing clip volume levels. To hide clip volume levels, deselect Show Clip Volume Levels in the View menu. (A selected item has a checkmark next to it; choose the item again to deselect it.)

3. Position the pointer over the end of the clip until you see the pointer change (shown below).
4. Drag the end of the clip to where you want the audio to start or end.

Tip: To hear sound as you change the length of an audio clip, hold down the Option key as you drag the end of the clip.

When trimming a clip, keep in mind that iMovie HD only hides the sound you don't want to hear and doesn't actually remove or delete it. If you trim away too much, you can always choose Edit > Undo to cancel your change, or extend the clip back to the desired length by dragging one of its edges in the timeline viewer.

If you need to remove audio in the middle of an audio clip, you can split the clip where you want to remove audio and trim the ends of the new audio clips. For more information, see Related Topics below.

Fading audio up or down

You can make sound fade up or down within an individual audio or video clip. For example, you can turn down the volume of a music track when someone in a video track begins to speak, or boost the volume of someone's speech if the recorded volume level is too low.

To fade audio up or down:

1. Click the Timeline Viewer button (A, shown above).
2. Choose View > Show Clip Volume Levels.

A volume level bar appears in each clip in the timeline viewer.

3. Click a point on the volume level bar where you want the volume to change, then drag the marker (B, shown above) up or down to adjust the volume.

You can see the percentage you've raised or lowered the volume of a clip in the clip volume field at the bottom edge of the iMovie window.

4. To specify where and how gradually you want the volume change to occur, drag the square marker (shown below) in any direction.
5. If necessary, repeat these steps where you want to bring the audio back up or down. You can click the volume level bar multiple times to adjust volume up and down at multiple points during a clip.

To remove a volume marker, select it and choose Edit > Clear.

Tip: When fading audio up or down, it's a good idea to zoom in on the timeline viewer. To learn how, see "Showing more detail in the timeline viewer" below.

Tip: You may find it useful to adjust the volume as the movie plays. If you adjust a marker during playback of a clip, the movie pauses and then begins playing again at the point where you made the adjustment. You can continue to adjust the sound until it's the way you want.

5. Text, Titles, Credits and Transitions To add text for title screens, general film text, or credits, click on the editing toolbar (three over from "clips"). Here you will find menus for Titles, Transitions, VideoFX and AudioFX. 

When making a title, the first thing to do is decide how you want the title to appear on the slide (do you want it to bounce, roll, fade...etc.). When you click on the various options, they will preview their effects on the screen to the left.

Notice the choices you have:

1. the style in which the text appears
2. the text itself
3. color and font of text
4. speed and timing of the text
5. whether you'd like the text to appear on a black slide (check "over black") or over an image or video segment in the video (uncheck "over black")

Transitions are the way that one video clip or image changes into another. To add a transition, click on the transitions tab at the top of the Editing menu window (to the right of "titles"). Again, clicking on the various effects will demo them for you in the video pane to the left. Once you've found the right transition effect, click and drag that transition to the space between the appropriate clips.

6. Saving and Exporting 

To save your video, click File--> Save Project As, and then enter the correct info. 

To export your video as an actual video file, and not just an iMovie file (which you won't want to do until you're finished editing, unless of course I made you paranoid with my save-your-work speech above) click Share--> QuickTime. Then you're ready to upload it to YouTube or whatever you like! Keep in mind YouTube limits your upload to 1 gig or 10 minutes, tho there are ways of compressing videos with a little googling. 

That's it! Now that you understand the basic components of the program, you're ready to make your cinematic masterpiece- have fun!