When you first create the new line you can mouse over the names of the cities in the upper left of the screen. That will bring up an icon that looks like a train manifest with a pencil and you click on that to set the number of cars.
When you first create the new line you can mouse over the names of the cities in the upper left of the screen. That will bring up an icon that looks like a train manifest with a pencil and you click on that to set the number of cars.