Along with the S Video adapter you will need two audio cables which supply the left and right channels on your TV.

You can buy a cable which will convert a standard 3.5mm jack plug (suitable for plugging into your PC's sound card) into two (left and right channel) audio connectors which you should be able to plug straight into your TV. There are more sophisticated setups available if you have a surround sound setup, but that will suffice if you just want sound from your PC through your TV.