It seems that the plugin does not permit users who are already registered to link a social media account with their current profile.
So, for example, since I am the administrator, I obviously have an account on my site. When I choose to login via facebook, rather than successfully logging in, I am merely told that my email address is already in use. I ought to be able to login with my site credentials, go to my profile page, and choose to link my facebook account so that I can use Fb to login in the future.
When will this be possible? Or Has anyone hacked together a way to do this?