HTH:
1. Get a good quality cable with a 1/8" (Mini) stereo plug on one end, splitting in two RCA plugs (labeled L/R) at the other end.
2. As with all Hi-Fi equipment, caution should be exercised during connections. Turn the power OFF for all gear until you are certain the connections are correct.
3. Plug the 1/8" end into the Line Out of the sound card.
4. Plug the RCA end into the CD input of your stereo (observing Left & Right orientation).
If you have a 2 channel input (L, R), you will connect the Line Out jack from the sound card to your stereo using a cable that splits into RCA right and left for your stereo. If you have 4 Channel input on your stereo, you will connect the Line 1 Out and Line 2 Out (if your sound card is so equipped) using 2 cables that split into RCA right and left for your stereo. If your stereo has 6 channel inputs, connect the same as for 4 channels, leaving the Center L and R channels unused (they will be rendered through the front speakers).