To start you need to create multiple layers. Each layer will become a separate frame in the animation. Since each of my frames will also have individual layers themselves, I'll have to make and flatten each one individually before I begin animating. Once the frame layers are created, you need to create each frame through the animation window. To assign a layer to a frame, it simply has to be the only visible one when the frame is selected, therefore two or more layers could also become one frame if needed. This is the bulk of the process, after each frame is created you can control the time delay from frame to frame and whether the animation will loop or not. All this is done through the animation window as well. Finally, you can save the animation as a layered Photoshop file, and export it as an animated GIF, HTML page, Flash, or Quicktime movie.
http://www.mediacollege.com/adobe/discontinued/imageready/animation/layers.html

