The most direct, reliable way to link a soundbar to a TV is via an HDMI cable. Simply plug the soundbar into a power outlet ...

HDMI ARC removes the need for an optical cable and allows you to send audio ‘downstream’ from a compatible HDMI socket on your TV to a compatible HDMI ARC socket on a soundbar or AV receiver.

There's only one HDMI port on the Arc, so the soundbar's Dolby Atmos support depends on the capabilities of your TV.

Regarding the ARC port, as far as I can tell, the point of it is that video passes through the port to the TV, while audio is returned over the same HDMI cable to the soundbar.