I don't know your exact set up, but I believe you can either just plug the audio cables (Red/White) directly into your system and then select that source on the device. If you have the standard cables, you can "peel" the red/white from the yellow to give yourself the extra length you need. If they are component cables, the red/white should be separated from the video (because red is used on both), though depending on the brand you might need a cable extender to reach the receiver.
Or your TV could be like mine, where everything is plugged into the TV (PS3, 360, Wii, Cable box, even an NES) and then have a single audio cable (coaxal) on the output of the TV going into your receiver. Without knowing what your exact setup is, it's hard to know what the best way to do it would be.