I am on a german layout, so a few words might be different for you than my translation :)
Setting
-> Basics
--> Applicationdomain: Enter here the domain you have uploaded your game to
--> Facebook Integration
---> Website: You need to insert a website, even if it does not exist at all
---> Application on Facebook: Secure Canvas-URL (Enter here the path to your game, starting with https://)
And that's all... nothing more I did :)