Link to Facebook in the Profile area

Hi.  I'm just setting up my forum, in the hopes of moving a FaceBook group over to it.  There, to my surprise, in the profile area is a button to Link to FaceBook.  Clicking on it, I get a pop up window.  In two browsers (I'm on a Mac, so sometimes I need to switch browsers to get some features to work), the window just stays empty.  In another, it gives me (after some hang time) a sign in window.  I signed in, and it got busy going blank, and that was it.  Done, it said.  I checked on FB, and there's no sign of any activity from the forum. 

What's this supposed to do?  Is it not working right, or is it a browser issue? 

Thanks in advance.