Devendre,
I don't have any specific documentation to send you about how to award on a successful registration after invitation. My best suggestion would be to look at the existing AUP plugin that does that. My guess is that it is triggered after the user registers automatically and then looks in the database somewhere to see if that user was ever invited by another user.
If that's the case, you could copy most of that functionality and check the #__jfbconnect_requests_notification table and check if the user that just logged in has a Facebook ID that's been sent a request before. In that case, assume that that request sender should get an award. If you get some code going, we can gladly help take a look or provide suggestions.
Finally, the "Destination URL", is where the user that is receiving/accepting the Request will be sent when they come to your page. That's good for sending them to the home page, a specific "Welcome from Facebook" landing page, or whatever you want.
I hope that helps explain,
Alex