If you haven't noticed you are able to connect your forum account to your facebook account now.

This was added more for new users to save them having to sign up.

If you do want to connect your facebook account to your current forum account then you can do so by going to your User CP and scroll down to the bottom of the page.

There really isnt much reason to connect your facebook to your forum account, but as i said it is mainly aimed at new users.

The bridge is called YAFB and can be found here for those of you who want to know more about it. YAFB - Yay! Another Facebook Bridge - vBulletin.org Forum

/Lapta