This download looks like a save. You need to place it in your saves 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.
Mystic Omen, MED.BOALI, Suprise!, Nairod_Ave, valegoru, medenüz :D, the d3signated driver, Fire_Tank, Darkoraxe, furkankozoglu415, susamuru0039, ekarizam80, aimbatman31, YkazdA, Yerald 1212-k, nevadatantan0, Yunus8253, Reysavick, omid.abdulwahidjan, edraggon099, oliver_cyr, LIL PEEP, com.antilles, w a v e, skullslater12, AmFoxine, HappyTurkey KeyDrop.com, Toni Makoroni, kemalbey506070, davidedwards2346, wrtd314, LeSaucyBoi, uauanisabucken, Raphael Petrovsky, gojanporras34, keremsuumerr, SG86, GR4NDM4ST3R, irisha.voloshina.69, jaygamer10177, josealejandro35000000, CORONA peek keltoşşşşşşş, 2241586939, kinayalperen, Panteralandia, Miguel Tg, dewataelektronik, MarcosFLAWBRAIN, MotoMurderRR, LordSkill +911 others