If it's your computer speakers I suggest you read the manual for the answer. Perhaps you plugged them into the wrong port. Or, you need to instruct your computer to play through the speakers - again read the manual. Or, type into your search engine: "computer speakers not working" and see what you can find.
You're going to have to give more details. Are you sure everything is plugged in okay and the setting on the computer are matched up correctly?
Add your voice to the conversation. Click here to answer this question.