Photoshop :: How To Import A Picture And Convert To A Layer?

I want to make a simple animation from 3 pictures (gifs saved on my computer). I understand that I have to get these 3 pictures to be layers but I can't work out how to do that. One tutorial referred to Image>convert to editable layer but I don't see this option on my menu (using CS2). I have to admit to not having mastered layers properly yet.

I would be so grateful if someone could give a step by step description of how to import 3 different pictures and somehow get them into one animation. The ability to make simple animations would make an enormous difference to the project I am working on.