Okay, so you know how to edit your signature?
Click on your username (For you, that would be Fluffy)
There will be a bar on the side, Click on "Forum Profile Information"
Scroll down until you see "Signature"
From their, you can upload an animated signature on a site, such as Tinypic.
Once you get on, you'll need to paste in the BB Code. It should show up on the side when you upload the picture from Tinypic.
Make sure if it's an animated GIF or something, you click on "video" instead of "picture" when you upload your gif.
Hope this helps.