Choose the Facebook Cover option in the left menu to preview what your video will look like in the 820×312 frame. Add padding, reposition, and crop the video so that it looks like you want it to, then click “CREATE” to process your new Facebook Cover. Kapwing’s resizer has a trim video feature built in, if you need to shorten your video.
https://www.kapwing.com/resources/how-to-make-a-facebook-cover-video/

