To install these custom maps:
1. Extract all .bsp and .nav files to your Team Fortress 2 maps folder
   (\steamapps\common\Team Fortress 2\tf\maps\), (or select tf2 in library, right click library/cog on the game library page, Properties, Installed Files, Browse... then find the file path as previously described)
2. Restart TF2 if it's running
3. It should work