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

Spinosaurus55, @TheOrangeGuy101.V2, Lacia ハロー, ogperezrubio, УГАНДА НАКЛЗ, Cordialkid, IzzyM, Saint POTATO®, thrdrkdragon03, ajcoollittlemanjr.2006, Undertow, The Chef Dogg, monkey775681, DarkExile, Cliffton, laptop.a.mann, alexkohn03, dannyrp00, kokot, bega5966, Mango, thewingedporpoise, Jay_Dubbz, superthugjetli, ArrozConLeche, S̸̨͕͌̽ȏ̵̰r̶̜͆a̸̺̐, gamermatti06, , adi_bedaru, FLYlas, FLYlas, wolverine041269, Terufus, ZedEXX, Irocron™, thsniperxavier486, sahil.findlay, TheRealJesus, galvinr, galvinr, overlordg1799, tr011yt199, Polski_Max, 音Temperament律, serhangkkaya, Kraken, NOTHING, Panda, juanomar.ascencio, [HR] Chief SuperVisor Owner +4414 others