FREE - In Google Play
FREE - in Win Phone Store
I am assuming you can't find the button, but since you give not the slightest clue as to where or when you are trying to do this, I can't do much better than to tell you to flail around until it strikes you in the face. If you gave more elaborate information than "this sucks" there is a great possibility your situation might not be hopeless.
If I login to my Facebook acct and go to chess.com, it's not there for my online games. If I go to chess.com, then login through Facebook, it is there. I don't understand why the difference.