Simply install JFBConnect just like it's new. Our installer will update things automatically and you shouldn't need to reconfigure anything. We always recommend double-checking that things are setup as expected after you install, including any new features, but it's meant to be a very smooth process.
If you have your Subscriber ID set in the JFBConnect -> Configuration area, you can also use the Joomla Update Manager to automatically update JFBConnect without having to download it from our site.
I hope that helps, but if you have any questions, just let us know.
Thanks,
Alex