This download looks like a lua file. You need to place it in your lua 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.
[COV]NV Fumer, rbhbkkn.kmrjd, Vurv, Dimi4ik44, TheRogueCoder, Dusty, mossesx, RaCc0oN \ keys-store.com, [INC]Be1zebub, pazuzu2010, "TheGamerBay", АNTIM, AlexALX, Firefucks, djmartin779, Shanker Jr, whomst'd've | Stai, Gamecrafter, sneakyrat, CoolD @ omni-games.net, Brad Darkstorm, ᗰIᑕᕼᑌ ᑭᒪ, 111a