We've added the ability to upload videos in Desmos classroom activities. Make sure you are logged in and simply head on over to teacher.desmos.com/custom. Click on "New Activity" to start creating a new lesson. If you'd like to add a video to a screen, click on the "Media" icon.
Click on "Choose a file to upload" and select the video from your device. (At this time, it is not possible to embed videos from other websites.) While the video is uploading and processing, you can continue editing your activity.
Once the video is completely ready, you'll be able to see and play the video within Activity Builder. If you'd like to see what the video will look like from the student side, click on "Preview" in the upper right hand corner of the editor.