Aaron,
If you're doing a real migration where you've simply upgraded your existing site to Joomla 2.5, leaving the tables from the Joomla 1.5 site intact, there isn't anything to do. Simply install the new version of JFBConnect for Joomla 2.5 and your configuration will automatically be detected and used for the new site.
Hope that helps, but if you have more specific questions on what to do, we can always help you in the process.
Thanks,
Alex