Help for Modding and Mapping
While creating a map in the MapEditor is pretty straightforward, the scripting and bounding it all together into a playable package, are not always that easy, especially if you have no idea how.
The Map Making Help page contains a lot of guides to clarify all this.
Creating buildings, objects, units, skins and so forth, is called modding. This process can be time-consuming and getting it to work fine, often demands devotion and knowledge.
A lot of useful information on various parts of modding can be found on the Mod Making Help page.