How do you eject a disc on a Mac computer if the icon does not show up in the Finder or on the screen?

Although I use PC's, not MACs, there should still be a small hole in the CD drive itself.

You should probably power down the computer before attempting this.

GENTLY insert a straightened paper clip into the small hole in the front of the drive. This should release the drive latch, and the drive should be able to be opened manually to remove the disk.

These manual release holes are very handy for removing CD's that were left in a drive when a computer dies and will no longer power up.