NeuroTec Collection - AIR by Hoffa

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

bastyili, kaisensteitz, adriel, prrotroll123, *ŋℙÕŋ£ℙ*, StormTrooper626, kadazelmat3, xxalexkillerxx1234, bosps2, reteps4002, antorjuan, Vite, omardv_01, Alfriiki, mtootoo827, V3ronese, TavaMammaTeica, breezyxkillerx, deltafour21bravo, BlackGhostTR, hassanrubbani2006, isenthebis, caseycsnider, alek.belous0v, Valenzuela88, SoupCan blw.tf, promasterpice22, lestercruz277, ็็็็็็็, texugueiro, Gambaruby, giustomax, edwinapr27, R0UT1N3, overwatchaltaccoun, Taboulé, ✪Zenixッcsgocases.com, Schnitzel, mogami, ariannunez2003, nesoyuncu, MrKoto, Toadiiii, Pippoo, TheThirdCraig, rexobib875, erikfig12, patrikcauan1, Redoko, animacionesstudioshd +4850 others