(1) On the subwoofer's rear panel, press and hold the pairing button until the LED  turns fast, flashing white.
(2) To enter the subwoofer pairing mode on the soundbar, press and hold the bass button on the remote control for more than three seconds. Then, press VOL - on the remote control.

On the soundbar LED display:
→ "SUB PAIRING": The subwoofer is ready for pairing.
→ "SUB PAIRED": The subwoofer is connected.