Can some one tell me where I can find materials about Learning Agent

I am new to unreal engine.
Currently, I am doing project with Machine Learning. I made a behavior tree for NPCs and I want them to enter battle mode when they approach the player at a certain distance. And I want to train myself for the fight.

And so I do not know how to do it. I’ve read all the official documentation about “Learning Agents” but I still haven’t figured it out.