Besides having Bluetooth your LG Smart TV should support LG Wireless Sound Sync.
Depending on the TV model you might be able to connect a Bluetooth keyboard, play music on the TV speakers from your phone or connect to Bluetooth headphones.
To check if you have that option.
Press the Home button on the TV remote
Click on the Settings icon (top right corner)
Click Sound, then click Sound out. By default the Sound out is set to TV speakers.
Click the LG Sound Sync (Wireless) and the Device selection pink button will appear.
Click the Device selection pink button and the TV will search for Bluetooth devices, so make sure your Bluetooth headphone is in pairing mode.
When the device shows up on the TV screen, click it to stablish a connection.
When connected it will appear under paired devices.