Hint: It’s not easy. Plan to rewrite. Learn how to block your scene (as in the theater/film term). Make sure the scene works as a scene: It advances the plot or characterization and has a beginning, middle and end.
Spend time learning about the fighting style, weapons (if there are any), potential wounds that can be inflicted, etc… I also suggest the voluminous @scriptmedic blog for understanding wounds and injuries. (The blog is being discontinued, but the many, many posts will be kept as a resource and the blogmom has written several useful books for writers needing medical information specifically for writers.)
I will also pass along one tip our own Graphei gave me that came in hella handy (even though my two fighters were Force users because I’m SW trash through and through): When two characters are fighting, they aren’t going to be physically able to hold full conversations. If you need to have things said, there will need to be breaks in the action, or you’ll have to move to internal monologue or have your omniscient narrator say the things. Your participants will be too busy getting winded.