Apple computers feature recessed slot-loading disc drives. The iMac disc drive is located on the right side of the computer, above the SD card slot. Before you can enjoy your favorite CDs and DVDs, you have to insert them into the disc drive slot. According to Apple.com, the iMac only accepts "standard 120 mm (about 4.72 inches) round discs. It does not accept smaller or irregularly shaped discs."
Locate the disc drive on the right side of the iMac, above the SD card slot.
Position the CD so the label of the disc is facing toward you.
Push the CD into the drive slot until your fingers touch the edge of the iMac. The iMac will catch the disc and pull it the rest of the way in.