You may now link your account to Facebook properly.
The facebook icon will appear in the upper right corner.
When linked you can make use of the facebook integrated features such as sending your threads/replies/blogs straight to your facebook page, liking various forum elements and probably other features I've forgotten but it'll be sure to remind you of.
You can either perform the link from the Connect button up or Add/Edit the link from your Settings page under Edit Connections.
*Note there seem to be some quirks in how some browsers behave with the features. Opera in particular doesn't like to acknowledge you're logged in but still gives you all the features while Chrome seems to be fine.