Add Facebook login to my iOS Pirates game.

I have a game on iOS, Pirates, that was written awhile ago (not using ARC). It's not on the store now. I did user registration using the device id from Apple, and since that's been deprecated and I want users to be able to transfer their accounts between devices I want to create a login/registration system. I think this would be easiest with Facebook login. On the server side, I have a MySQL database piratesiphone which contains the user's data and I have a database globaliphone which contains the user's device id, email address and which of my apps they currently have. (I also had apps Ninjas, Kingdoms, Aliens, Vampires). The piratesiphone user's table contains a column for the globaliphone id. Please be familiar with the Facebook SDK for iOS. Please be familiar with PHP/MySQL. You can write this code in Swift, Objective-C using ARC, or without ARC. It's up to you. It has to work with my non-ARC Objective-C project. You will also be using PHP/MySQL and SVN, so please be familiar with them. Right now, if the user isn't recognized, they are sent to the PickUsernameViewController where they enter their username, and their they are sent to the PickClassViewController where they pick their class. Before this happens they should be presented with a Login with Facebook button on a new view controller. Their facebook credentials should be sent to the server, and if they're recognized they can begin playing with that account. If not, when they register after picking their username and class, their Facebook credentials should be sent to the server.