Measure the distance between your PC’s current location and your home audio system. In order to connect the computer to your home audio device, they should be within 12 feet of each other.
You will need to purchase a 3.5mm stereo mini-phone plug to dual RCA jack stereo cable. On one end, this cable will have a plug that fits into the headphone or speaker jack on your PC. The other end will be stereo RCA connectors that will plug into the corresponding jacks on your home audio system. There will either be a set of two plugs, red and white, or three, red, white and black. Make sure the cable is long enough to reach from the jack on the PC to your home audio system.
Connecting the PC and Home Audio System
Before getting started, turn the volume all the way down on the home audio system and then turn off both the home audio system and your PC. Plug the headphone end of the cable into the corresponding jack on your PC. This is typically a light green jack, but may be a different color or not colored at all. Make sure it is the headphone jack. Next, plug the RCA ends of the cable into the home audio system. Make sure you plug the connectors into Input jacks and that the color of each connector end matches the color of the jack in which it is inserted. For example, the red connector should be plugged into the red-colored jack, and so on.
Turn on the PC and then turn on the home audio system. Open a music file on your computer or find some streaming audio online. Choose something that will play for a while so that you can have time to adjust the volume and other settings on your home audio system properly.
Turn on the home audio system and select the proper setting depending on which input the RCA cable is connected to. For example, if the input says "AUX," be sure to select the home audio system’s auxiliary option. Gradually increase the volume on your home audio system and make any other changes you desire.
Aside from using a mini-phone plug to dual RCA jack stereo cable to connect a PC to your home audio system, you may be able to use other types of connections that can provide even better audio from your computer. Read the Bright Hub article Home Theater Connection Types to learn about other types of connections you might be able to use, such as HDMI or component surround. HDMI vs S-Cable will give you more food for thought, and Using PC Audio Over HDMI will show you how to connect home audio to a PC using an HDMI connection.