On some forums, they allow you to change your display name (the name thats shown on the forums, not the one you use to login) yourself.
But that appears to be disabled on this forum. (Profile -> Modify Profile -> Account Related Settings)
Your only option is to PM an admin, and hope they are not to busy, and take the time to do it.
This IS NOT an open invitation to spam admins, be respectful as always. (As you should to everyone)