Your Playfab account is for managing your cloud saves across your devices. You're only required to make an account if you want cross platform saves If your device is lost or you change devices you'll be unable to retrieve your saves without an account. It's highly recommended to close your app using the back button or the escape button to allow the game time to save your game to cloud.
To access your account, open the account panel in the settings.
Create Account - Here you can create an account. You'll only have to do this once, and you'll only need to login if you are on a new device. If you are already logged in, you won't see this option.
Login - Here you can login if you are logging in on a new device. You won't see this option if you are on an existing device.
Send Recovery Email - Use this to send an email to the address you entered to change your password.
Default - The default checkbox determines your default save file. If you have one checked, when you start the game, this save file will attempt to be loaded. If it fails or you don't have a default file selected, you will default to the locally saved game.
Opening a save will present you with your cloud details and your local details for comparison.
Delete - This will open an option to permanently delete the save. Once it's deleted, it can't be recovered.