|I don't think you can do it with just a cable. You need something like this adaptor :|
You would connect an AV cable from yellow composite connector of the adaptor to the yellow AV input port of your TV
That will take care only of the video signal. You still need the audio cable you've already purchased. and it would connect from speaker/headphone socket on the laptop to the red/white audio inputs of the TV. You then select the AV as the input source on your TV controls.
Goin' Fishin' (Some day)