Dell OptiPlex 755 - Manual (Page 123)

5. Check the documentation that accompanied the drive to verify that the drive is configured for your computer.
6. Align the shoulder screws on the optical drive with the shoulder screw slots, and slide the drive into the bay until it clicks into place.
7. Connect the power and data cables to the drive and to the system board.
Always connect the optical drive SATA cable to a system board SATA connector that is labeled with a number higher than those connected to any hard drives
installed in the computer.
8. Check all cable connections, and fold cables out of the way to provide airflow for the fan and cooling vents.
9. Replace the computer cover (see Replacing the Computer Cover ).
10. Update your configuration information in system setup by setting the appropriate Drive option (SATA-1, SATA-2, or SATA-3) under Drives. See System
1 optical drive 2 shoulder screws (3) 3 shoulder screw slots (2)
1 power cable 2 data cable 3 SATA optical drive connector