what i think you are trying to say is you have a cable with a 3.5mm audio jack on one side and the white/red composite plugs on the other.
you have it plugged into the headphone out port on the pc, which should be fine for exporting sound, provided the pc recognizes that you have something connected. play something and see if you're getting sound but just not hearing it (try looking at the audio devices window)
as for what ports you have it plugged into on your tv? i have no idea. make sure they are audio-in ports and not audio-out. you might need to configure your tv properties to make these the default audio ports which may be why you hear no sound. i can't tech you how, you need to figure that out on your own.