IMPORTANT: PLEASE close Left 4 Dead 2 before install.

Download and extract the zip folder.

Put the vpk in the Left 4 Dead 2 addons folder. Below is the typical location for it.

C:/Program Files (x86)/Steam/steamapps/common/Left 4 Dead 2/left4dead2/addons

Make sure the map is checked in the addons section of your game in the main menu.

Join a server and type "!mapvote" and select a custom map to vote.