This download looks like a map. You need to place it in your maps 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.
sebastian2003elcapo, Falucii, Masoud, *DnG. | V I O L E N T O * ^ !, The Fire Pyro, maxitoroblox6, San :3, renan3989, tizianaperez, deadfox430, danutangelin75, Haydee_Lover, silasricker, thamkst83, gscsb00, nicolevm2907, keduxgamer777, ultrix, BlueBlurSonic, just4musicfl, Thatonek1dd, dusql, JUNKRAT R, alphagoldytde, santaolalla2004, hanpop15, yousef.akbarzadeh98, francois_so08, felipeamaro02, noelaugusto, joaobonnie, seiyaht3, korbenmbond, fomfon191, abd.omari99, drgultekin0, X | Dan, aleamgabriel01, nihao20, Spungly, Alanzito, migueltellomosquera, bayloncrogers, anpan3chibi7, yantomaskovic.abcdegf123465987, emeraldcraft7482, emeraldcraft7482, tdog8785, manogorreja962, P.H.7( ͡° ͜ʖ ͡°) +963 others
