joker_mk_vs_dc_player.zip

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:

• steamapps
  • common
    • garrysmod
      • garrysmod
        • addons
          • Joker MK VS DC player <-- Addon folder!
            • e.g.
            • lua
            • maps
            • materials
            • models
            • etc

• Joker MK VS DC player/
  • Joker MK VS DC player/
    • lua/
      • autorun/
        • Joker_MKVDC_S-low.lua
    • Materials/
      • Models/
        • Player/
          • Slow/
            • jamis/
              • mkvsdcu/
                • joker/
                  • slow_joker.vmt
                  • slow_joker.vtf
                  • slow_joker_bump.vtf
                  • slow_joker_buttons.vmt
                  • slow_joker_clothes.vmt
                  • slow_joker_clothes_fx.vmt
                  • slow_joker_clothes_green.vmt
                  • slow_joker_eyes.vmt
                  • slow_joker_flower.vmt
                  • slow_joker_hands.vmt
                  • slow_joker_head.vmt
                  • slow_joker_head.vtf
                  • slow_joker_head_bump.vtf
                  • slow_joker_shirt.vmt
                  • slow_joker_shoes.vmt
                  • slow_joker_socks.vmt
    • Models/
      • Player/
        • slow/
          • jamis/
            • mkvsdcu/
              • joker/
                • slow_pub.dx80.vtx
                • slow_pub.dx90.vtx
                • slow_pub.mdl
                • slow_pub.phy
                • slow_pub.sw.vtx
                • slow_pub.vvd
                • slow_pub.xbox.vtx

Bubbafrog, CrILL3r, korylopez870, cauappereira.s15, Elix1r, somazalucio2, korylopez870, korylopez870, maximoalex565, Victor h1g, colebihh, manueloncio2006, Komari studios on vr, Komari studios on vr, akroursof, kjunio123, rigby700, Nopphumz, denizagah, NazTho_Shitpoxt, Pyronite202, ᴮᴬᴰʙᴏʏ, ✧Kᴏᴋɪᴄʜɪ Oᴜᴍᴀ, miguel918.h, _ECLIPSE_, hexer54539, hexer54539, jeremiowo g4skins.com, Leoplace71, *****gamer64jason, elgabigoleador3443, kubalat2008Key-Drop.pl, Benjaminplay11, MR.LazyBones, Solid Green, DARBY, rieyantocopier, zeilkid13, h4h4, dj.gamer.chris75, Gamesofking12, Mr.Eduh, soloturkx00, pedrohphgrwph, The Real Fat Cartman, Rubeus Hagrid, zaneaj217, gunersimal, kacperwojtarowicz672, Some Random Idiot +154 others