Tablet Facebook App Help[

[Shirley Stodghill]

I just recieved a Xelio Tablet for christmas and I am using the Google Play App on it. I'm playing Candy Crush Saga and Pet Rescue Saga through the facebook apps, and I have 15 dollars on my facebook account from a previous gift card. Everytime I try to buy or pay for something it goes to my google play account and asks me to redeem a Google Play gift card or add a credit/debit card. I want to use my Facebook Account Balance, how do I do this?