HaloMods "Classic" Read-only Archive

Hey guys. I'm new to modding and I downloaded a skin and went into serenity everything was filled out so I click on apply patch and it says "Source file not found." What do I do?

Select the source file, lol

Just select the clean Map you are modding.

C:\Documents and Settings\LocalUser\My Documents\beavercreek.map

Thats what it says in serenity for my source map.
I'm a a little retarded so It takes a while for me to understand things.