Well are you talking signature or the text over my shiek avatar?
well here it is for both.
Signature: If you set up a photobucket account (click here for link) you can make a pretty awesome sig, of course, all for free.
But for text: go to your settings, and hit on the side bar "Edit Profile". Then at the top, there will be a blank type-in-box, Type in what you want it to say, Mine says Heroes can become legends.
Hope this helps!