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.
MOSTAFA HRN, masascuate666, ethan.tom.hunt.cruise, alex_valenciana, valentinostardust, Neondromeda, kitlucky88, loureirochristian92, loureirochristian92, Barturenxxx, jeffersonshalom94, gregoryaltuve05, Dedlus52, hellwolf2, xdarksiderx1, играб-и ГРАБЛИ, MØI, MØI, codallywicked, mix.shoes12, Nekyto, HG | Talbot, HG | Talbot, HG | Talbot, sla00364, Rubeus Hagrid, Sage, raiden.storm14, selsoft63, Genji_overwatch, erikvagyok99, aubrianna, matdes, slotbk123, azov_wars, VitorGomesHD, Hunter_Kyro, ultima_sword, mxcgoodco, aljavier900, zigortfurkan, OH SHIT, Harambe Uchiha, Tal Rex, edgaralves2004, manjoon, gmangp1453, TW 大河, NOT THE BEES, tkn2512 +148 others
