CD changers allow you to insert and play back the audio of several, if not hundreds, of CDs (some CD changers have the capacity of playing 200 or more CDs). Depending on the equipment hookups on your changer, you may be able to install an aux input. Aux, short for "auxiliary," is a connection method for hooking up external devices, such as an MP3 player. If the CD changer has a standard RCA audio input option, you can adjust it to an aux connection in only a matter of minutes.
Connect the RCA ends of the RCA-to-3.5mm cable into the "Audio In" ports. These ports are typically located on the rear of your CD changer.
Plug the 3.5mm end of the cable into the headphone jack on the device you want connected to the CD changer.
Power on the CD changer and the 3.5mm equipment. Select the "Playback" option, then press the "Play" button on the connected equipment. The audio signal from the hooked-up device begins to play through the newly created aux connection.