This download looks like a map. You need to place it in your maps 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.
ya.javorsky2013, O_O, Phailnwza567, glob, koroglualperen014, Sydr0M, ZeroXenix246, folktvone, CathedrylVanHellsing, MLG-KAM!KAZE, Pandora, [FLC]Sandro, laszlomruczler, Combiner, chooncho2004, docteurx1980, piy piy, Dethcross, stefan.03, GerCobra | Basti, Ptah, dariotrnka, DEADLYTR1GGER, zerographics, csgobounty.com csgowitch.com, HauDes, danhhuynh250, say something, Ma name m JeFf, [Lord]-Put!n, startcravt2018, Cheesus, Miku Hatsune, hover35 Farmskins.com, Alien On a Treadmill, ＲＡＺＥＲ516, 士林金城武, Realxy, OLDxSTYLEZ, magicdrop.ru, 人卜L卜, abdalrhmankhaleda_k, (-C-)Logge, andrey, ezequiel.diaz.puertas, Uloksu, lhagvajavpro, MEGAT_T, Nacpac, MonsterGwardian +5418 others
