AnimationEvent, Collider, OnTriggerEnter logic?

Good day everyone!

I'm making a TPS melee/hack n' slash game but I have this problem. I have a player character with a punch animation. I have not-so-much understanding on how AnimationEvent works. I'll have to call something like "damaging function" exactly when the animation reached the keyframe where the character punched with fully extended arms (If there's collision with an enemy character of course). My problem is, I don't know how to sort things out (scripts, colliders, animation). In short, I do not know how nor where to start. Step-by-step aid is really what I need. But any help/tip/tutorial links will be very much appreciated! Thank you!