Start by selecting the Effects Workspace
Effects allow you to make adjustments to your clips that range from distorting your clips, to reducing hums in the background of your audio, to adding a drop shadow to your video.
To access these effects, look to the bottom left of your workspace and select the Effects tab.
Within this tab, there are two folders that involve effects.
To apply the effects, open one of the folders, grab the effect you want and drag it onto the clip that you want.
You can change how the effect changes your video under the Effect Controls panel at the top left of your workspace.
Effects will be rendered in realtime, if you add too many then the system will get bogged down.
Once you've committed, you can build a preview by pressing "Enter" on the keyboard.