Event not playing

Hi, I am using the trial version just to learn this software before starting my new radio job !
Problem is, I have been trying to set up an event (a music or a VT for example) to air at a certain time and when the time comes, it just gets added to the list, but never gets played.
Could someone please explain how to set and event (something that needs to go on air at a certain time).
I would be so thankful !