Lol ok. Go into User CP, then Edit Signature.

Copy this in - [IMG*]http://i2.photobucket.com/albums/y1.../FFFreakSig.jpg[/IMG*]
But make sure you take away the *'s otherwise it wont work.
If you want your signature centered then use this -
[CENTER*][IMG*]http://i2.photobucket.com/albums/y1.../FFFreakSig.jpg[/IMG*][/CENTER*]
Again, without the *'s. When you are writing a post, make sure the "Show your signature" button is ticked.

For your avatar, save the image to your computer, then go into the Edit Avatar in User CP, scroll down to "Upload an Avatar From Your Computer" locate your avatar, then click Save Changes. Simple!

Hope that helped, Voodoo