Not a stupid question.
Considering that you have your TV hooked up I take it your TV has RCA connectors.
All you need to do is go to a big CD or Hi-Fi store and get the necessary cable depending on the output (RCA or analog) your soundcard has.
If your TV has altogether 3 RCA connectors you must get a cable that outputs to stereo.
Hope thats clear enough, ask if I must explain something.