Connect an account to unity?

First off, I had no idea where to even post this.

So I'm developing a game in which I want it to connect with google and have the user log in. If he logs in his data starts syncronising*. Any ideas??

*Downloading if there already is, Uploading if there isn't.

 

You will need a backend to manage all your account info and data synchronization.
You can play around with MySQL and some php.
After that you will need to create a web services for your account authentication.
Once authentication is complete, you need to make another web services to check your local data authenticity. If it is OK you synchronize if it is not auto ban player or notify admin that this is a dodgy account.