EditWorld is a bit dumb – it can't remember if you've started a new map after you'd loaded some other map before.
So, before you do anything, choose "Save Project As" from the File Menu and make sure your new map is saved under a new name. This prevents any previous map from getting overwritten!
Design considerations
Before we can truly begin though we need to make you have a checklist of what's required...
You should have an idea about:
what you want to do
which tileset you wish to use
name for your map
number of players
if you want to include scavengers
If you have all that then your ready to continue. You should be familar with all of the commands now so creating a new project should be of no problem. Make the map the way you want, lay any objects, buildings, etc. you want. Put down the tile you want to use. If your comfortable try using some of the edge brushes or changing the tile types. A few things to double check on your map though before you export it.
Each player has 1 truck and 1 structure
All building must have one space between them
You must have 1 gateway on your map, even if there is no need for it
Do NOT place objects near the edge of the map or it will crash. Oil resources are the only thing that will not crash the game. Though you will not be able to use them. Always place everything 4 tiles away from the edge of the map.
Make sure you have either 2, 4, or 8 players on the map and they are numbered as such
when you export your map make sure to only include letters. No numbers or symbols
If you include scavengers they must be marked as player 7. They also require 1 oil resource with derrick, a power generator, and a factory
Once you have all these items done you should be able to export your map with no problem. Hopefully you wont run across any problems, so good luck and happy map making.