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.
cv83027, NPC, marlonfelixbueno, cyns | TP-N.co, arepafrita, ꧁༒☬KaLSHinKOv$☬༒꧂, out20zxxx, williamreilly, edwardvictoriano77, omardv_01, SG86, markgamert112, RUMPLESTINKI, utahraptor72, BlackGhostTR, khoadangtran820, Valenzuela88, ็็็็็็็, M1lkyPen, FG-<nightmare>, kmcgmc, [ Atago ], four_tony, tutorialesypartidas10, CaptainL10, emrhn3834, aynurdogan476, SquidTheKid, LemonadeNaruto, ridwanandrianou, ZeusDestroyer_89, Rene, georgio10el, Влад, the.coolsniper, lightblaze894, Dar1us Kincade, mlthebest94, Ursão Peludo, nigersnitch, LynCz, tonnum321a, mcgian2018, adam.lomia, josemiguelochoa91, sdkndkn cs:gocases.com, bruhrelol, Trần Dần, owlthingy, TeğmenKağan +1818 others
