Sure! I'm assuming you want all users to require approval, not just those that register through Facebook. If so, in the Joomla User manager, go to Options and set the approval/activation mode you'd like to use. Then, in JFBConnect's configuration area, make sure the "Skip Joomla Activation" setting is disabled.
That should make JFBConnect respect your Joomla configuration settings for user activation.
Hope that helps, and if you were looking for something else, just let us know.
Thanks,
Alex