The best way to hook up a soundbar depends on your TV and soundbar, but there are four primary ways of connecting a soundbar -
HDMI: This is the preferred method as it provides the best audio quality and supports features like ARC and eARC. Connect one end of the HDMI cable to the back of your soundbar, then connect the other end to the HDMI ARC port on your TV.
Optical cable: This is a common method as it is compatible with most TVs and soundbars. Connect one end of the optical cable to the back of your soundbar, then connect the other end to the optical port on your TV.
Using a RCA cables: This is a less common method as it is not supported by many TVs and soundbars. Connect one end of the RCA cable to the back of your soundbar, then connect the other end to the rca inputs on your TV.