You were right first time, there is an Audio Out socket on the card. Audio In would serve no useful purpose on a TV card.
From the Specs:
This card has the potential to turn the back of your PC into a rat’s nest of cables, having no fewer than 6 external connectors. They are: FM Antenna, TV Antenna, infra-red sensor, audio out, S-Video input and composite input.
You need to connect the Audio Out to the Line In of of the Sound card and then configure both the TV Card and the sound card appropriately.