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:
Don't know where the Garry's Mod folder is or how to extract zip files? See more useful installation tips.
2b, Allvaro, th2drago0, Ninian948, Click, Self Proclaimed God, OasiZz, gimclab228, extreamgamex, Julien Levy, JayyJayyHD, Geforce Ryan, VLADOS_papiros, , Oogie Boogie, Xuryai, [SUP] SlenderBoi, Harzm, Sedrowow, EliteSniper, nono19777, Hari Seldon, Neno Noros, Funny, Not So Salt, |Z| DuckRevoe, Bart La Buse, Wonkkk, lucas93123456789, ChickenDestroyer21, jonesboy1999, PoloMaster, FrankGammer, Ink Sans, Gamerfrankstar, gassed up, jquub4343, ТРИГОН, OSSI.DK, minefalling, LaurBerg, xder, CRAZY_TACOz, victormiles31, LIL Sande, zev0k, Lixou Geek, Angelic Ross, /FIFFmim/, kaum zeit ab jz +1759 others
