There are many ways to eject disks:
eject key in upper right of keyboard
select disk in Finder and select Eject from File menu
drag disk in Finder to trash, which turns into Eject icon
eject button in DVD Player (which is what I guess you tried)
if disk displayed in sidebar of Finder windows, eject button next to the disk
Have you tried everything and the disk still doesn't eject?
Steve