Before you start...
Some things to note, this is not the only way to support Modding in your game. It's also not the only way to support Lua Modding in your game. In fact, using this mod to create your Modding API will likely take a lot more work than using native scripts for Modding. However, the advantage using luaAPI over native scripts is that the Lua code is sandboxed. No one can access parts of the engine that you don't explicitly give access to.
If you are looking to make your game using Lua or would like to support Modding without worrying about a sandbox, check out one of these projects: