Tom,
The SCLogin module works with JomSocial. The Login With Facebook button will register the user in JomSocial (if you have the JomSocial profile plugin for JFBConnect installed) and can be configured so that the links for Register for this site, etc all point to JomSocial.
As for your Error Occurred message, I mentioned that in email, but will respond here as well.. I think your App Id is incorrect. Fix that, and you should (hopefully) be good to go.
Hope that helps,
Alex