Eg: Cut, Cut and so on have the function of intercepting still frames (pictures) for cover more conveniently.

Computer editing software

For example: the cover of PR, fcp, etc. Use the frame capture tool in the same way, and then put the captured picture at the beginning of the video (the cover is the first frame of the video).

Of course, you can use graphic design software (ps) to make a picture with the same size as the video, and then import the picture into your video editing project and put it in front of the video.

If there is anything you don't understand, you can ask in detail.