Help create.

Hey everyone, I've decided to create some custom units. And I figured you guys might be able to help me out! Please don't ignore this thread! Could you please tell me how to create at least one unit? It doesn't necessarily have to be for a castle. Just a standalone unit. What programs are needed, what knowledge of scripts is required, etc.? As I understand it, a unit is several images and a file with its characteristics, all packed into a DIN or several files, right?:confused: Help, please!!! P.S. Preferably (if it's a program), include a link. Thanks in advance.