Unpack the CD-ROM. Make sure at this stage that you have your anti-static measures in place, and even briefly make contact with both hands on the metal of the case to make sure.
Using the IDE Configuration Pins set this device as a Master. In some cases, particularly with DVD or CD-Writers, it is necessary to select Slave for best performance.
Read our IDE configuration crash course.
As with the floppy drive, you will notice, on the front panel of your PC case, there is an opening the same dimensions as the front panel (if there is a plastic cover plate fitted, just gently push it out from behind.) Slide the CD-ROM into the opening backwards such that its front panel becomes flush with the front of the PC case.
Once fully inserted, there should be some fixing holes inside the case such that you can secure the CD-ROM drive to the case. Use the 'fine threaded' screws for this.
Once inserted, use fine-threaded screws to secure the drive to the case.