Unfortunately, Valve has not yet enabled custom maps to show up on the campaign selection menu even if they are installed. nav files and copy them into your maps folder.
The guaranteed way of installing a map correctly is to take the. This won't work for every map because not all mappers package their zip files the same way. Everything should automatically go where it's supposed to. zip files on this site are meant to be installed to your left4dead folder, which is usually C:\Program Files\Steam\steamapps\common\left 4 dead\left4dead.
