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.
BombermanMaldito, BombermanMaldito, E7ajamy, PATIENT: Death, GOD USOPP !!!, fuky.martin, 3zo0oz11223, Survive the attack, mr.gamerrr, Alan ElGamer, AlexKiller007, muhabishar, MaXiK <3 Šťyl - MucQ :'D, Hydra(Beast), Mister Lunacy, DarkSniperTR, Sokkah Abdelkader