To get the TV sound from external speaker, Connect TV and External Speaker (Sound receiver or home theater) with any of the below options:

Option 1: With HDMI Cable-ARC Port  (Best way to setup)

Connecting your sound receiver to the TV with HDMI will give you the best possible audio. HDMI cables transmit sound digitally, which makes everything crystal clear.

Step1- Connect one end of HDMI cable at 'HDMI ARC' port in TV and another end at 'HDMI ARC or HDMI Out' port of external speaker (or Home theater / Sound receiver)

Step2- Select your sound receiver as Sound output by utilizing the Quick settings option. You can also navigate to Settings, and select Sound. Next, select Sound Output, and then select HDMI Receiver option.

OR

Option 2: With Optical Cable  (Great way to setup)

An optical cable is also another way to connect your sound receiver to your TV. This type of cable is similar to an HDMI cable and transmits digital sound, so you can hear every detail. 

Step1- Connect one end of Optical cable at 'Optical' port in TV and another end at 'Optical' port of external speaker (or Home theater / Sound receiver)

Step2- Once the physical wire connection is completed, use your TV remote to navigate to Settings, and select Sound. Next, select Sound Output, and then select Optical option.

OR

Option 3: With Bluetooth  (Good way to setup)

It doesn't have the same sound quality as HDMI, but everyone loves the convenience of Bluetooth since you don't have to worry about any cables. The main challenge with Bluetooth is that connections can disconnect or become unstable if there's some kind of disruption, like a power outage. Bluetooth is still a nice and easy option to have, though.

If you want to connect your sound receiver via Bluetooth, first switch the pairing mode of Sound receiver (Refer Sound receiver user manual)

Once the soundbar is in pairing mode, use your TV remote to navigate to Settings, and select Sound. Next, select Sound Output, and then select Bluetooth Speaker List or Bluetooth Audio Device, depending on your TV model.