Firstly, the video is converted into AVI format and opened by UleadGif software, and then every frame of the image opened by UleadGif is saved by PS.

Use PS to paste the avatars you want to replace into the animated pictures one by one.

Create a new file in UleadGif, set the size and frame number, then copy and paste the PS modified pictures into the frames of the new animation file in sequence, and finally save them as Gif files. .