gm_lonehouse_day

This download looks like an addon. You need to extract the downloaded zip and put the addon folder in your Garry's Mod addons folder. You should end up with a directory structure similar to below:

• steamapps
  • common
    • garrysmod
      • garrysmod
        • addons
          • gm_lonehouse_day <-- Addon folder!
            • e.g.
            • lua
            • maps
            • materials
            • models
            • etc

• gm_lonehouse_day/
  • info.txt
  • maps/
    • gm_lonehouse_day.bsp
  • materials/
    • maps/
      • gm_lonehouse_day.vmt
      • gm_lonehouse_day.vtf

Player-0, matheussantanasantiago1.0, __, archicastor1, facundo.romano18, mister_wayne, juandavidarias2002, Alex