combine_apc.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
          • APC <-- Addon folder!
            • e.g.
            • lua
            • maps
            • materials
            • models
            • etc

• APC/
  • info.txt
  • lua/
    • autorun/
      • vehicle_combine_apc.lua
  • materials/
    • models/
      • combine_apc/
        • apc01interior.vmt
        • apc01interior.vtf
        • glass.vmt
    • VGUI/
      • entities/
        • fixed_apc.vmt
        • fixed_apc.vtf
  • models/
    • Vehicles/
      • combine_apc.dx80.vtx
      • combine_apc.dx90.vtx
      • combine_apc.mdl
      • combine_apc.phy
      • combine_apc.sw.vtx
      • combine_apc.vvd
      • combine_apc.xbox.vtx
  • scripts/
    • vehicles/
      • fixed_apc.txt

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