These are "view only". To make a copy you can edit, click "File > Make a Copy" to save to your Google Drive.
You can make a copy of any of these backgrounds to use in your own Bitmoji classroom. Click the slide you wish to copy, then hold down the keyboard keys CTRL C.
Then go to your Google Slide Show and hold down the keyboard keys CTRL V to paste the copied slide.
You must create a free Snapchat account to make an animated Bitmoiji. Once you have created one and saved it to your device, go to https://www.unscreen.com/ to remove the background.