Official comment
Unfortunately, Facebook changes their interface and allowed options often. We have an updated forum article on it at https://ontraport.zendesk.com/entries/58786854-Facebook-Integration It is working as of March 3, 2015.
In the comments is a video showing how to create the "Connect with Facebook" button in the Facebook Developer's section. The video is a rough draft and hasn't been adapted by our video department to show in the actual forum article yet, but it should give you an idea.