First, make sure that consist mode is deselected (radio button in bottom left flyout menu) then double click on the coach whose number you want to change. A new flyout menu will appear in the top right (strongly advising pinning it with the pin icon in the top of the flyout). In the middle of the flyout is a text box with a series of characters in it (eg. 15880156123A) which correspond to the unit number, coach number, and destination. You can consult the manual which cane with the addon to find the destination list. Hope this helps.
"I don't make mistakes. I make prophecies which immediately turn out to be wrong." "And now, excuse me while I interrupt myself" - Murray Walker OBE
Student of Mechanical Engineering at the University of Nottingham (loosed upon the real world for a year)