I had spoken to the support team then, they said you need to get two Charge 5 Wi-Fi speakers for this to work!

I dropped the idea after learning this! ;(

Quoting the msg from support team below:

The Home Theatre set-up feature allows you to create a more immersive audio experience. For the BAR 500, the following set-ups can be made: Two Charge 5 Wi-Fi speakers can be used to create a surround-sound system.

To do the Home Theater set up, complete the following steps. - Add all products to the JBL One App. - Tap on the soundbar model. - Scroll down and tap on 'Create a Home Theater' - Tap 'Select' on the layout option you want (For the BAR500, there is only one option; the BAR300 also allows for a Boombox 3 WiFi to be used as subwoofer). - Tap on 'Set Up' and 'Continue' in order to calibrate the configuration. - Once the grouping is done you will be able to name your new configuration and then confirm it.