Your TV seems to have a headphone jack on the back. It's the only audio output. Connect it to the analog audio TV input. You will need a cable with 2 RCA plugs at the HTS end an a stereo 3.5mm plug at the TV end.
You only need this connection if you use the internal TV tuner or sources with analog AV (like an old game console or VCR) that are connected to the TV directly.
You will get a better result connecting all your external sources directly to the soundbar HDMI inputs and connecting the HDMI TV output to an input on the TV.