On your home page, just under where it says Welcome, about 4-5 lines down says Update your Profile.
Once you click on that a new screen pops up, the 4th section down says My Aquarium Info. Most people put the tank size, extra equipment, and # of and types of fish/coral they have in their tank (you can click on my "myinfo" tab to see what I am talkin about).
Others put their info in their signature section instead which is the next section down from the Aquarium info.
HTH