Track Junction Questions

How do I change switch a track in the game TS12?I am running on the SBCX Route I am at a junction.The arrows are green & red.The track I want to switch that arrow is in red so how?Do I switch that track it says a train.Is blocking that junction but there is no train I made a session with no AI.Trains I need to know how to switch.That track so I can head east.

As far as I know it is the train you are driving which has locked the junction. You need to back off from it as you are probably to close to it to make the change.