Use the simple World Editor tool and other advanced developer tools to create your own world, whether it's fictional or based on a real world location. You'll find help and advice here.
Iv managed to get markers into the route, although not named yet, but the background is like this, iv done what it says in the RS documentation by loading the deafult Kuju materials etc etc and then exiting and entering again and no joy.
Iv also tried to get the DEM data to load but thats for another day
I had the same problem. I uninstalled RS and installed it again, and then it worked fine. I must have done something wrong in my early days poking around the filesystem exploring before the devtools and docs were released.
This is a known bug, you need to select the Object Select Filter (small cube) in the middle left-hand flyout panel and select Kuju and RailSimulator in the right-hand flyout panel, then exit the simulator, on reloading your new route you should have pristine green texture. You will then need to reselect your name and route or whatever so that any markers, etc, you have created will show.