NeuroTec Collection - HAWX 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

Truxxor_01, p8071853, [Noëlle], ThePatriot, , palestineforever, anesmohbhfs, 2Krunchy, wids, PlodixGamer, munmichal, Boogers, course1x9765, Juan pitorico, glorywolf23, ElMesiasZaka, CGaming, Vladímir Ilich Uliánov, ZeroSilkson, SlavicKing, Seeargee, dinhndrw, DBENFLEN, kostik0s_2017, kostik0s_2017, kostik0s_2017, Aldana donscheff, zudokai98, 3374634752, afhyib45 tastygo.su/free_skin, afhyib45 tastygo.su/free_skin, abuluzus, Faker, milaninwar, plywood [ SGR ], Star17, ask012509, davidmancebopc, Phoenix, knathanwilson, iCamp, tomastitovanerio, XLEBYIIIEK, persatiago, segurahanley, segurahanley, Retr0, zamzammubaroq28, mahdiibazobandii, pickleman +4231 others