Spawning Trains - What Am I Doing Wrong?

I thought it wasn't working because choosing a "bad" train for a route so.... her'e what I'm doing but it just seems to not work (for me). I must be doing something wrong!
Main Menu -> Choose Blackpool Route. -> Free Roam
Pick a statio e.g. Preston and Play
Wander to platform and by pressing TAB key spawn a Class 142.
So far so good. How do I set the route? Pressing '9' to get map I can click on train I've just spawned and get a pop up box "Sandbox Options" 3 options available "Set Path", "Remove Train", "Close"
Close is default as highlighted white. Remove Train works. BUT Set Path is greyed out and unavailable.
How do I pick a path to get it to allow me to choose? Apologies if I am missing something really obvious!

 

Have you sat down inside of the Train before you press 9 for the map ?

 

You have to sit in the train first before you can set a path for it. TSW needs to know which train it is you want to set the path for.

 

Ok Thanks. Will try that