Merge the GameData folder with the existing one in your KSP directory. KSP will then load it as an add-on. The source folder simply contains the source code (in C#) for the plugin. If you didn't ...

Marni Rose McFall is a Newsweek reporter based in London, U.K. Her focus is on U.S. politics, social affairs and popular culture. She has covered fashion, culture, art and music extensively.