I have also a leadteck TV-tuner card,
i have to connect the green connector on the back of the card (outside computer) to the line-in connector of your sound card. (als outside computer)
Did you read the manual?
i myself did some rewiring to connect the outside plug of the TV-tuner to the internal 3-pins line in of my onboard soundcard, because i really need all my connections for 5.1 output, to my surround tuner.