C:\Program Files (x86)\Steam\SteamApps\<YOURNAME>\garrysmod\garrysm od\lua
Put in there your script.lua or whatever, just remember what you name it.
Open game
Use a bypasser if needed
open console and type
Lua_openscript_cl script.lua
script will then run, chances are if it's hera or blue or something you need to bind the menu
bind l "+blue_menu"
Voila.