Connect the speakers to the receiver. Plug the black, or negative, end of a speaker wire into the "-" "Left Speaker Out" jack on the receiver, and then into the speaker's negative, or "-", jack on the back of the speaker itself. Connect the red, or positive, speaker wire to the "+" Left Speaker Out" jack on the receiver, and then into the speaker's "+" jack. Repeat this step for the right speaker as well, while using the receiver's "Right Speaker Out" jacks instead.
Plug the 1/8-inch end of the 1/8-inch-to-RCA cable into the audio source's "Stereo Out" that you are wanting to send to the speakers, such as your MP3 player or computer. Any audio source that features a 1/8-inch mini jack for output will work, although the jack may not be labeled on your computer. Usually the jack will be green in color, or have an icon with an arrow pointing outward.
Connect the RCA ends of the same cable to the receiver. Plug the white, or left, connector into the receiver's white, or left, "AUX IN" jack, and then the red into the red jack as well.
Plug in the stereo receiver and audio source's power cables, power on the devices, then set the receiver to "Aux Input." Most stereo receivers allow you to choose what audio is being sent to the speakers by way of pressing the "Source" button on the front on the interface until "Aux In " appears on its screen. Now you will be able to hear the audio coming through the stereo plug into your speakers.