You have iMovie on your iPads. It will definitely help to learn the basics of that application.
You want this Book on your iPad. I know; a book... Not Kidding
iMovie for iPhone & iPad - 15 Power Users Tips & Tricks 2017
Download any footage you don't have from your shared folder in Google Drive
Use your storyboard to create a rough cut of your video.
Add B Roll into your rough cut using the trick shared below.
*A rough cut is where you have put the video files into the order you’d like them, but you haven’t completed the scene or movie. When the editing process is over, and it's time to start on sound design, we call it a fine cut.
iMovie lacks the awesome multiple timelines that Premiere has, but a lot of students like it because it's a lot easier to use.
To the left are some tutorials that should really help you use B-Roll in iMovie like a pro!
Like on Mac, you can easily add a cutaway footage or b roll to your movie on your iPhone or iPad
Firstly, have the main video clip of your video loaded up in a project in iMovie on your iPhone or iPad.
Hit the plus icon to select the b-roll footage, you can choose to add another video or a still image as your cutaway.
Once you find your b-roll footage, tap it and then you should see a box pops up with icons for plus, play, and three dots, just tap the three dots and select Cutaway.
Now the cutaway b-roll footage should be added and you can see it above the main track, here you can still edit both as you please.
There are a lot of places on the web to download open source and public domain B-Roll, but the school keeps blocking them. Here are some sites to try:
Media College -::really lame site warning::
Beachfront B-Roll (Has nothing to do with the beach... just random B-roll clips)
Shoot some random B-roll...