I didn't make it!
I downloaded paintball gulch, ppf-o-matic, and winrar but i dont know how to make paintball gulch playable in halo, can someone who has done this before help me with a step by step process.
Well, if the mod is a .rar file, then install winrar (if you haven't already), right-click the .rar file, and click 'Extract to _name of file_' This creates a folder with the mod in it. Then there will be a _mapname_.map file in the new folder. Copy/paste that into a folder called 'MAPS' that is in your Program Files/Microsoft Games/Halo folder.
If it is .ppf, then open ppf-o-matic and click the box next to 'ISO File'. Browse to Program Files/Microsoft Games/Halo/MAPS and select the map that the mod is on (it will be 'mapname'.map.) Then click the box next to Patch and browse to the .ppf file of the mod. Then click Apply and it's ready to go.