I need help on a stop motion project for science I just don’t really understand what to do and I can’t use and app the teacher recommends because it cost money and the other apps I can add the picture

I need help on a stop motion project for science I just don’t really understand what to do and I can’t use and app the teacher recommends because it cost money and the other apps I can add the picture but I don’t know what to do after that and this is for applied academy science