How do I let users add their real name in ()'s next to their username?

[JoeJack101]

How do I let users add their real name in ()'s next to their username?

On some vBulletin forums, I've seen something like this for the format of usernames next to posts....
dark_knight872 (David)
Username (Real Name)

How do I get it to show up in threads like that on MY vBulletin forum?

Here is the URL of a forum that's like this:
http://forums.govteen.com/showthread.php?t=241222

Here is the URL for MY FORUM:
http://www.ugissues.com/