Its rather simple actually.
Insert the CD or DVD into the SuperDrive
You should see an icon appear on the desktop like when you mount any other drive.
Simply right click on the icon and choose erase.
NOTE: I’ve had OS X not recognise a DVD and only give me the Ignore and Eject options. If I choose the Ignore option I don’t get an icon to be able to do the steps above. I haven’t worked out what to do there yet. Possibly something with diskutil from terminal……