Hmm... Animations are a bit tricky, I haven't really had occasion to experiment much. See if this is what you want:
1) first you'll need a new document obviously. Settings don't matter.
2) We now need to decide what to animate as requested, we'll just make a flashing square.
3) Since we now what we're doing now, we now need to make the the frames for the animation. The easiest way to do this is to have one layer for each frame. Go ahead and create these layers now. Your layers palette should need only three layers for this: the top layer should be totally yellow, the middle orange, and the bottom layer red.
---Side note: if you don't already have your animations bar up, go to Window->Animation and the top of your screen.
4) We now have everything we need for our simple animation. In your animations palette go to the all powerful 'three parallel lines' button in the top right of the palette to open the menu. Simply click on "Make Frames From Layers" and viola! you now have a (very rough) animation.
5) There should be a play button (the little triangle like on a VCR), near the bottom left of the palette. Click this button both to start, and stop your animation. If your result is (miraculously) what you were looking for then well done go to step 7. If not continue to step 6.
6) (optional) If you're reading this, then I'm assuming there is something wrong with the timing of your frames either they are too long, and the animation appears to not be animated, or they are too short and your animation is too painful to look at. Don't worry, that is what the number under each frame is for, it can say anything from 0.0 sec. to 10.0 sec. click the number to bring up a little menu with varying times, Feel free to experiment here, as this setting is more a matter of taste. I ended up with my red frame at 1.0, and my two other frames at 0.2 seconds.
7) Animations can't be saved the normal way, or you'll just end up with an still image. You'll need to go to File->Export->Render Video, after the intimidating window pops up, just name the file in the top blank, and that's it, just accept any other settings.
Whew, that should work. As you can probably tell, photoshop isn't really made for animations. If you are wiling to spend the time though it is possible to even make professional looking files.
) I left one out! I also would very much like to know how to use animation. I'll try for a simpler example here: Say I want to make a web background that is solid red then flashes to orange then to yellow, and back to red again.... just a flashing background basically. Details help, I AM blonde