When you create a train, you also need to name the towns it will visit during
its run so SwitchList knows which freight cars may be picked up and dropped
off. The Train Stops Window appears if you press the "Change Stops..." button
in the Trains tab.
To describe a train's trip, build up a list of towns in the right hand side representing the stops it will make in order. Select a town from the list of all towns on the left, and press the "Add ->" button top copy it in as the next stop on the train's stop list. If you make a mistake, select the incorrect town on the right hand list, and press the "-" button.
Trains must start and end their journey in a town with a yard. If the current list of stops does not include a town with a yard, the dialog box will display a message explaining why the path is invalid.