1. Open Train Simulator's 'Editors & Tools' utility.
2. Click 'Activity Editor'.
3. Click 'File', then 'New' and choose the relevant route.
4. In the 'Activity Name' window that appears, leave it alone. It doesn't affect path making.
5. In the 'Player' section on the right hand side, click the 'New' button.
6. In the menu that pops up, click the 'New' button under the heading 'Path'.
7. Type the same name into both the 'Path Name' & 'Path Display Name' windows that pop up.
8. Now, zoom in and out of the route map using the mouse and/or the tools box (has direction arrows and zoom options).
9. When you locate the place you wish to start, right click on that spot and select 'Place Start Point'.
10. When you locate the place you wish to stop, right click on that spot and select 'Place End Point'. If you cannot get the highlight to go the way you want it to, right click and select 'Toggle Start Direction'. A simular princible applies for points. If you are making a path to simply explore with, you can place the 'End Point' a small distance from the 'Start Point' and Train simulator will let you drive past the end point for as long as you want.
11. Now fill in the 'Starting Location' and 'Ending Location' boxes and click the 'Leave Path Editor' button. It will ask you if you wish to save. Click yes.
12. Now, close everything and load Train Simulator. Click the relevant 'Starting Location' and the correct direction and enjoy the path(s) you have just made!