If you still need the help..
go back into Photoshop. Open the non animated part of the sig, merge all layers so its one layer (but make sure you don't merge a BG, cause you need that transparent part for your fire.
Then stick all 10 or so layers of fire you have into that as well. (where they need to be layer wise, all aligned and and whatnot.) So when you have that all set, you should have a non animated sig w/fire.
Now click that button that imports that psd into Image Ready.
Bring up the animation palette.. and just do what you did before with the showing/hiding of layers to make your animation.
If you still need help, I can open image ready and give you more detailed instructions, but you already made the fire part by itself, so I figured you know how to make the animation.. just getting it all there together