Sorry for the crappy editing in advance, was in a rush before work.
Getting an entire authentication flow setup in 15 minutes or less!
In this video, I go through a detailed, step-by-step introduction to getting started with Firebase Authentication in Unity3D. This is meant for beginning students of programming and game development, but if you're an old codger/developer like myself, you might still find it useful, if a bit rambly. Follow me on Twitter: KyleTheCoder. If you have questions or comments, you can find me there, or in the Facebook Unity Course Community group provided by Ben Tristem from Udemy, and on gamedev.tv. In the future, I'll show you also how to use the database part itself directly - but I should warn you, it will be basically just as easy as this was.
The Unity Asset Package for Firebase that I mention can be found here:
https://firebase.google.com/docs/unity/setup