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.
AIM|BOT, Hellfireraz, thanapum0807, 熱盛, WavyRed202, Chernobyl, Kenshiro244, bogery0704, teresamenge, bendymolina, kdogg3127, MaesOhm is a Furry, mr_gg48, mrchip0601, zariharizanov, zariharizanov, AnthonyPog, Cmoney2149, Suzuki423, lobotomek, lobotomek, Sennin, ^oKµjo, 乱丢大, Ecaten, Gabrielgamertv1390, Gabrielgamertv1390, Hyman_Roth, chapmanmillie, danieldrakonunek, Link_elHeroe_temporal, joelincon1234, Demonic Assassin, pinkmethflamingo, coltonwhitmore, segapopcorn09, yonatan.tevel, MafianAS, matthewmatt123455, Amun, Andrey_291004, ThrustAttic335, capitaine poulet, isaidemiliano, luisdp006, Stane., LgB, tigrisjozsi, Hermes, ElManruel +1047 others
