The invitation configuration is setup through the module itself, and has no required additional application settings. The most important is the "Invitee Welcome URL". This is the URL that user's will be sent to if they accept an invitation from your site. Generally, this should be set to your home page.
If this isn't what you're looking for, or you're still running into issues, post a link to a page that you have the Invite module set up on, and we can help diagnose any issues from there.
set the application to run facebook invitations (mod_jfbcinvite ).
