• In scenario tools select Track infrastructure (semaphore icon) and choose Stopping Point.
• When you place it yellow line appear - you have to select place on rails (arrow appears like AI spawn point) where you want to have stopping point.
• When you are satisfied click with LMB. Be sure that this arrow is in right direction (it has to be same as train direction) - you can change direction with ctrl (or shift)+click.
• Last thing is name this point - you do that if you double click on stopping point icon (looks like light bulb or speaker) - last two lines are what should interest you (Marker name and Internal name). It is good if it has same name.
• Last thing is that you have to select this stopping point from destination list (f.e. if you created stopping point at station XY platform 2, you have to select from destination list stopping point@XY platform 2)