JFBConnect lets the connect to your site with their social network account in multiple ways, and it's very configurable in the JFBConnect settings to allow/prevent some methods.
If the user doesn't have an account, they can use the social login buttons (Google/Microsoft or others) to have a Joomla account automatically created for them. From then on, they can login with that social account. You can also configure JFBConnect to send them their Joomla username and password that was created so they can login with standard Joomla credentials instead of their social account.
If they already have a Joomla account (whether they created it or you, the admin, did), JFBConnect allows the user to 'connect' their existing account to any social network. To do that, they click the social login button (you should see these on this site by hovering over the My Account menu item in the top right when you are logged in). They'll have to approve your site to link their account. Once they do, they'll be able to login to your site in the future with their social network or Joomla credentials.
There's no way for you, the admin, to link an account to another user's social network account. The user needs to do that as they have to authenticate on that social network and give permission to your app, which only they can do.
I hope that helps explain things, but if you need anything else, please let me know!
Thanks,
Alex
Connect to Google after registration
