How to learn a new programming concept?

I'm a beginner programmer, and I'm curious about how experienced developers learn new concepts. For example, when you encounter something like recursion, OOP or even just a new function/library, what process do you follow to make sure you actually understand it? I'm looking for a framework or checklist. How do you know you've gone from "I read the explanation" to "I can confidently use this in a real project"? A few things I struggle with:</