Changing "tag line?"

This may have been covered already, but I'm clearly too computer illiterate to figure it out.

How do you change your "tag line" that's displayed under your user name in the forum? I simply have not been able to figure this out - but it's clear that it's something that can be done (and isn't a "rank" thing like on some lesser message boards).

Thanks in advance!

On the left of the screen click User CP then Edit Options. The second section has "Custom user title"