I got a new phone, how do I log back in?

You just need to log back in the same way you were logged in on the old device.

1) Open the game 

2) While in your garage, tap the Settings button 

3) Then tap on Profile 

4) Then tap Login with Facebook (or with Apple ID if that's how you logged in before)

Keep in mind. If you logged in with Facebook in the past and have more than 1 Facebook account, you need to be logged into the correct FB account BEFORE you log into the game.
If you are currently logged into a different FB account than when you created your account, it will not work.

You need to log into the proper FB account first and then log into the game.