Go to UserCP, choose Edit Profile from the menu on the left, scroll down a bit and under "Additional Information", the first thing is the WoW characters and how to fill it in.

Aha! I missed it the first 3 times looking through :P

For those that have not checked it out yet, in your UserCP, in the "edit profile" section, there is a place to list all of your in-game characters. Once added, they'll show up in your post user display (over on the left) and on your profile page. They are clickable and link to your WoW Armory.

That is pretty damn awesome. Thank you for this.