How to implement oAuth2 authorization in Spring-Boot + Gradle + PostgreSQL?

Question

PostgreSQL

I've been trying to figure this out for days now. Of course I googled, but the answers are either not obvious to me, or I did something wrong.
Main problem: I don't understand how this ecosystem is supposed to work at all. More precisely, I don't understand how spring-security-oauth should work. Already worked with oAuth2 itself, but not in java.
My vision of the situation at the moment:
1. In Gradle, just add the lines from here ;
2. And, in fact, that's all .. I don't know what should be in the project, what dependencies still need to be connected. Of course, there is wonderful documentation , but without an example I can’t understand how to make my authorization based on this...
I would very much like to get a better idea of ​​how to set up the whole thing for authorization through at least Google. At least some small instruction on how it should work ..