Normally you would just go to your User CP (
http://www.i-mockery.com/forum/usercp.php ) and then click on Edit Profile. From there it should give you the option to change your title. But yeah, as Boogie said, you weren't able to... probably because you're an old member and your account was moved to these forums. You should be able to change it anytime you want though now that Boogie fixed it.