M4A1 in Halo Reach (Campaign map included)

Backing up the vanilla maps

First, locate your maps folder under "Steam\steamapps\common\Halo The Master Chief Collection\haloreach\maps". Make a backup of all the maps so that you can always revert to the default maps.

Backing up the vanilla sound files

First, locate your maps folder under "steamapps\common\Halo The Master Chief Collection\haloreach\fmod\pc". Make a backup of the "sfx.fsb" and "sfx.fsb.info".

Installing the mod

This last part is pretty simple, in your "Halo The Master Chief Collection" folder just drag the "haloreach" folder from the mod into your game's folder and replace all of the files.

Installing the tag

Just extract the "memes" folder into your "HREK\tags" directory.