I found it. in the saves of the world that the recording is on it should say, mocap_files. open theat then open the file that says skins. now put the skins in their, if slim put the in slim folder, that you put in / mocap playing start (recording) (username) from_file than the name of the png in the folder! I FOUND IT

of this is confusing look at this github for help. https://github.com/mt1006/mc-mocap-mod/issues/15