This download looks like a save. You need to place it in your saves folder inside the Garry's Mod folder.
You should end up with a directory structure similar to below:
Don't know where the Garry's Mod folder is or how to extract zip files? See more useful installation tips.
Waffle The Lad, nok, FartNebuleuse, Galahad, house*****5904, kekoadybanez, russ, SLiGunner, spet ops skyler, NunQmad, 12th TimeLord, nadson_12fsa, Duality, PollakMc, qwer 123 bro, JSM-5GS, MaxiGrenon, Хозяин, money93577, ConfuseD, Cpt.Trace, Drifter108, madman.fa3, christopher525, chuckjoens11, Bob, Ermel{GER], Grigory Raspytin, PopsiclePete, dnzemrsrk, amir290904, Remis, ᶨᵘᵍᵍₑᵣᵑₐᵤᵗ92, ᶨᵘᵍᵍₑᵣᵑₐᵤᵗ92, ᶨᵘᵍᵍₑᵣᵑₐᵤᵗ92, efeufus, Skidaddle skidoddle, igrok, Hotrod, ᵖᵃᶜᵏᵉᵗ, ...:::HOFDOG:::..., ...:::HOFDOG:::..., Raptor, Whrite, BOLFIEBOLF, STUB., STUB., Strikker1918BAR, Fasteer, Caleb +7 others
