Hey Immy, sorry if i'll be answering the question for Rob.
On the top there's a link
"Profile". Once the page loads ... you'll see a lot of information you could enter and what not. Under your birthday option .. there'll be a button saying
"Edit Signature", click it and it should bring you a page where you could edit your signature.
If you want to add images. Just find the direct link to the picture you want to place ... if you have one yourself, just upload it to
www.imageshack.us and then copy the link. Once u have a link ... just write [img]
paste%20link%20here[/img] ... make sure there are no spaces in between.
Hope that helped

. Enjoy your stay!