I’m trying to make a simple AI with RL but can’t figure out how backpropagation works.

I already made a simple neural network and it works, however I struggle with finding a way to make it learn, I just can’t find any information about that, because most of the articles and videos cover only supervised learning which won’t work in my case, or don’t cover backpropagation at all.

I just want to see if there are any articles or videos that explain this thoroughly.