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.
domd31675, _temza_, tomascano.romani, gavintron99, graslukasz, wuki.vucko, denisalexandru00, M A C, arianasheghi2377, reephn, Mr Serbian, minerlorenzo, MCGamer2006, alejomolina, alejomolina, Lucas Camarotti, TKCOWO, herobrinevlog, d.lukasz05, Suzulaugh, +*Cute_Boy+*, timikunik2005, kriszimiszi122, romantyczka64, denisalexandru00, lmpzy, alexshulski, mjcvandyk, Blesk, demon spy, fenix2, cute.boyammar, silvasandro26061972, nica.alex.35, GENTLEMEN SPY[ASİL TR], TommygunJ, kriswertel, LAY-LAYLOM66, merritttrainboy, AtlanT, opposingforcegamer22, Julian Van, Julian Van, Xeonas, Xeonas, Raibowdash-zhenyacase, Creepygamer this is power, jackkeosodsay, ivan.vrbic646, GamingWolf500 +118 others
