I assume all you have is the LUA and not the modules that go with it, take the lua file and put it in your GMOD directory and inside the folder that says lua..
Open up the game, get Extreme Injector and install GDaap bypasser, inject it pretty straight forward, go back to GMOD, join a game and open console type lua_openscript_cl (lua file name whatever you called it) then click enter and to open it after that just click home or insert can't remember which..