Without model numbers we can't tell what connections you have.
If the TV has a headphone jack or analog audio output then use that. If it has speaker terminals you can use a speaker to line level converter.
If the TV has a digital audio output you will need a digital to analog converter.
If the TV has no audio outputs then you will need to connect your sources audio outputs directly to the HTS. You may need an HDMI input selector with audio extraction.