I've never done this but I would imagine you would export an image sequence from FC into a folder using Quick Time Conversion under 'export'. Mark your In and Outs. Select .png, and save the image sequence into a folder. Once in PS, open and create a new layer for each frame you want in the animation. Open the animation box under 'window' and select each layer in the sequence and how long you want it to stay visible. Then optimize it for the web, save it as a .gif and you should be set. Like I said, I've never done this but I'm guessing that is how it would work. Hope this helps.