Mary,
There's a few extensions that we integrate with that allow you to use their registration flows while logging in using social networks. Can you let us know what extension you're using for registration?
Beyond that, there are a few options:
* Create a new Social Profile plugin, which JFBConnect uses to integrate with other extensions. In there, that can specify another extension to use for the registration flow. That takes just a few lines of code. Additionally, you could pre-fill the registration fields in the other component, but that takes more code.
* Auto-assign registering users to a special Joomla user group. This is easily done, but would be a fixed group for users that register through a social network.
I hope that helps explain the options. Again, if we already support your extension, you may not need anything special.
Thanks,
Alex