Facebook Canvas URL, Secure Canvas URL

Hi, I am using buddypress default theme and i have installed Ultimate Facebook.

What I want is to let user log in to my website using facebook, but I dont know how to se the Canvas URL and Secure Canvas URL.

I am newbie, so have spent 6 hourse trying to find a setp by step guide saying how to create the files needed, what code to put inside and where to put these files.

When I try to log in with facebook I get "page not found".

Thank you very much!