Insert the two 1/4-inch cables from the 1/4-inch-to-stereo Y-cable into the "Master Out" jacks on the top of the Denon X100. If you are using the computer as one of the audio sources, connect the two RCA cables from the RCA-to-stereo Y-cable into the RCA jacks for either Line 2 or Line 4.
Flip the switch to the right of where you plugged the RCA cables in to "LN." (Skip this step if you used the 1/4-inch-to-stereo Y-cable in Step 1.)
Insert the stereo end of the Y-cable from Step 1 into the line-in jack on the back of the computer if you used the 1/4-inch-to-stereo Y-cable. If you used the RCA-to-stereo Y-cable, plug the stereo end into the headphone jack on the back of the computer.