You'd need an optical audio cable like https/www.amazon.com/AmazonBasics-Digital-Optical-Audio-Toslink/dp/B00NH11H38/ref=sr_1_1_sspa?s=electronics&ie=UTF8&qid=1510471229&sr=1-1-spons&keywords=optical+audio+cable&psc=1.
Then set to tv the digital audio as output and to the soundbar the digital audio as input.
From the tv's manual:
Connecting a device using an optical cable does not automatically change the audio output to the device's
speakers. To change the audio output to the device, do one of the following:
Use the Quick Settings screen to change to the connected device:
Use the Select button to select Audio Out/Optical on the Sound Output menu. (Settings up
directional button Sound Output ).
– Use the Settings screen to change to the connected device: Select Audio Out/Optical on the
Sound Output menu. (Settings Sound Sound Output).