Facebook Connect authentication settings are located in Site Manager -> Settings -> Security & Membership -> Authentication -> Facebook Connect. Before you start making the settings, make sure you have the right site selected using the Site drop-down list at the top left part of the page.
•Enable Facebook Connect - indicates if Facebook Connect authentication is enabled
•API key - key obtained during registration of your application on Facebook (as described here)
•Application secret - key obtained during registration of your application on Facebook
•Assign new users to roles - new users registered via Facebook Connect will be assigned to these roles
•Required user data page - URL of the page where the Facebook Connect required data web part resides; if entered and a new Facebook Connect user logs in to the site, their user account is not created automatically, but they are redirected to this page and required to enter some additional data (or merge with an existing account) using the web part