FirebaseUI Authentication provides the simplest and easiest way to add prebuilt UI and implement sign-in flow including OAuth providers such as Facebook, Google etc.
If you look at most of the web / mobile login screens, you will see the three most important sign-in methods such as Email and Password, Facebook and Google.
At the end of this article, you will have a fully functional sign in flow including login screen like the screenshot below with STEP by STEP Instructions.