Here is a link to the start of the process. It`s a pretty lengthy process, and has to go through the community. That being said, it is probably the most rewarding experience on Conquer Club! Good Luck with it and have fun. I hope to play on your map.
Go to this forum and start a new thread with the idea for your map. You want the graphics as fleshed out as possible to start, but leave everything editable.