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.
, yzengardiens, Jazzper, kaikejch, leon.zhnecz, Anstiméo [ק๏๏tเร], Adamska, DelKic Gamdom.com DotaX2.com, guillermobergh94, Milo, extrasven, kaikejcd567, PAGAN, Deimos, Stait x3, kaikejcd745, cosmicchristv, Døç†øЯ, ShaunDash, my.little.pony.and.dinosaur, zanofa88, SGC | Vicky (AFK), Loser, kaikejcd44, kaikejcd44, kaikejcd44, Xeno14, mr_nightmare, kaikerkj, univex_dark, Logan, ballesteroaxel173, The Super Shock Master, kaikejrd428, PyWoRLD, PyWoRLD, Lady Béchamel, olgaptic, marzluise, frenki05, DekSethmc, papa gabe, isaaclevyt21, John Mullins, gamerguy8973, romantyczka64, kefir4uk, roboticcyborg2, aquarianwarrior, berryarg +469 others
