Ultimate Facebook

Hi, I would like to know:

How can I allow old users to login via “login with facebook” link. Right now only people who registered via facebook have option to login via facebook as well.

Can I, and how can I remove default facebook login added by plugin and add manualy shortcode in the place I would like.

Thank you,

PS: I’m using plugin on blogg.pl/wp-login.php and blogg.pl/wp-signup.php