First you of course need a character for yourself with attack animations and whatnot. You need to add Image Points for the attack animations where the so-called hitboxes spawn at. The hitboxes are the invisible "bullets" you shoot from your hands, just like in real life (loljk). Then you need to add events that check animation frames. Like, when the attack animation comes to it's impact, check its frame number and set that into the event. Then add an action to spawn your hitbox to your image point.
Next add an event for your enemy to see if it's colliding with the hitbox. If the collision happens, make an action that removes the hitbox (if you are after realistic attacks), substract health from the colliding enemy and play sounds etc.
I can't give any examples since my only fighting game project with stuff like this is quite big already. As long as you've gotten around the logic how conditions, actions, collision and such works you shouldn't have hard times to get this working. Then comes polishing and making it look good. That's another story.
Just a hint: Make the hitbox remove itself after one tic so enemies won't be walking into invisible, floating punches your attacks leave behind. Also adding variables for the hitbox for damage and attack type (for different hit animations etc makes your work easier. Add events for setting the damage and type right after spawning the hitbox to control the power of your attacks.
Whoa, a long post this one... :D