Navigate to your MCC installation folder and replace the maps in the "halo1\maps" subfolder (make a backup first!).
For subtitles, you need to replace the initial_textures.s3dpack located in the "halo1\prebuild\paks" (again, make a backup first!!!)

Navigate to your MCC installation folder and replace the maps in the halo1\maps subfolder (make a backup first!).

For subtitles, you need to replace the initial_textures.s3dpack located in the halo1\prebuild\paks (again, make a backup first!!!)