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.
joalalfred21, [GGC](Ger)Alexander, Higgins, flocefai, Curry, Random Sans, Bio, Krzysiu, XAZOR, pacino80, Жмышенко Валерий Альбертович, Lehy, SealSAURUS REKTS, MateuszNEXT, Florian Bos, ❤ C R E O N I X ❤, fantome, MK | GalactiK cases2x.com, Mipastu, GreyNade, RobertMer, Thekodex12, Grozger Zasrogtiveslin, Richard Roy, DJReFor [idling], 18gradenbewolkt, João, Scoop, Fancy Mango, shixthug, civil rights leader flavor flav, haagse24uur, TwoFactor, PonyEB, Makarov, thewildbirdmedic, firefox450, ☯≤<Nikita>≥㋛♛☃ ✔, DarkAgeVenom, [=Elite=] Lukas ; Arts & Design, Philippe Théoricien d'Orsay fdp, KennyS, Prixi., kevin stan 06
