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.
lancethedankmememan2000, lancethedankmememan2000, ElChamoSinJuegos TwT, Coil The Sad One :/, re15revisited, Turrican2015 [FR], 1111111, phanshocraft00ara, XeroX, =ΡΡ= 419, miniditt, CONRECON, LuisMexElite
