strapless_boombox.zip

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
          • Strapless Boombox <-- Addon folder!
            • e.g.
            • lua
            • maps
            • materials
            • models
            • etc

• Strapless Boombox/
  • info.txt
  • materials/
    • models/
      • props/
        • boombox.vmt
        • boombox.vtf
        • boombox_blue.vmt
        • boombox_blue.vtf
  • models/
    • props/
      • Boombox.dx80.vtx
      • Boombox.dx90.vtx
      • boombox.mdl
      • Boombox.phy
      • Boombox.sw.vtx
      • boombox.vvd
  • settings/
    • spawnlist/
      • Strapless Boombox.txt

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