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.
TRIGGERED, Smeone retards, Table, [BB] Officer Boo, Grozger Zasrogtiveslin, Squishy The Russian Dog, ⓓⓔⓛⓣⓐⓜⓞⓓⓩ, Wirelex.exe, mj07619, Rocky2u, MonsterSpaghetti, MisterMelon, Axarator, Jack, John Cena, John Cena, pariksanz, Osama Bin Laden, T-Rex, arpee name, arpee name, Dark Cocaine, elt @ kralking067, Seal Lord, cheezrguy, DotEXE, theandrew61