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.
Austin5098, TypicalDad, ajsmommy926, ajsmommy926, xveb, Woozie, Ivan, CreonX, Sleepy Slime, 2EZ4JC, Loki Laufyson / Smitty Werban, Zytex, k_rauth29, Strelome, PM4444, Zerey_Tii, Pinaplle, gustito123, Джеб Керман, gamekiller 3.0, LIL YING YING CHING CHING, Issei, Pan Naczos, hollow knight, Suprise!, Ramo58tr, Yahzy, MIKO, Max, bister9999990, bister9999990, Doritos® Glimmer Flavour®, Watermelon, oops_wine, oops_wine, oops_wine, oops_wine, oops_wine, battlefilm052, ghostxxss54, Perry the Platypus, santinocabrera2510, Stealth, [102nd] Kebab, Osk_MyrKush, RobertB0ss, amador2323, АРТ, Lorenzo Baglio, Lonely llama +1880 others
