[Plugin: Simple Facebook Connect] How to know if user is logged in in FB

Hello Sir/Mam,

Please help me or give me ideas how to use Simple Facebook Connect plugin to know if user is logged in in facebook and has authenticated the the facebook app. Because I’m creating an online voting system and I have used WP Post Ratings. I want users to be only allowed to vote if he/she is logged in in facebook and has authenticated the app using Simple Facebook Connect plugin. I also want to know how to get the email address of the user using simple facebook connect and pass it to a php SESSION variable. Please I need help badly. Can someone point me to the right direction? 🙂