You will need an appropriate driver for the CD ROM in the extensions folder, like "Apple CD-ROM" or "Apple CD_DVD driver". Depending on the kind of CD you want to use you might need an additional extension for CD data format support. If the CD ROM is not supported by the Apple driver you either could patch the Apple driver using ResEdit or get some third party driver like CD ROM Speed Tools.

To put a driver into operation after moving it into the extensions folder you usually have to restart the Mac with the CD ROM powered up, except you use a tool like "Load a Drive".