It's called a signature, or sig for short. Read the stickies in the new enthusiast forum, such as the one titled "getting started in LS1tech" or something like that. And read the stickies in the other forums before asking a question. Oh yeah, read the stickies in JRP's sig if you haven't already found them elsewhere.
Go to user CP and slick on edit siganture.
I'll be at four years with mine in 11 days.