merging or upgrading account

Joaquin,
JFBConnect works great on sites that already have users. There are multiple ways that users can connect their existing accounts to their Facebook account. Once connected, they'll be able to log in with their Facebook credentials or their existing Joomla credentials. The main ways to let users connect are:
* When they login with their FB account the first time, if their FB email address already exists for a Joomla user on your site, their account will automatically be associated.
* You can use the "Normal Registration Mode" setting, which lets users see a registration form during registration. There's also a login form on that page where, if they enter their Joomla credentials, it will log them in and connect their accounts.
* In the SCLogin module, you can enable a setting to to show a "Facebook Login" button when the user is logged in via Joomla but hasn't connected that account to Facebook yet. When they click that button, it will log them into Facebook and automatically connect the accounts.

Hope that makes sense, but if you have any other questions, just let us know.

Thanks,
Alex