I want to edit settings on a map

There’s a map on Starcraft 2 called “Lordaeron Conquest” I want to edit it, without messing things up. I want it to allow free for alls, instead of making everything into two teams or 2v2v2v2v2. How would I do that? Also, what if I wanted to allow people to choose their teams, rather then “Good VS Evil”. Can anyone help?