Question: how to pair bluetooth headphones to galaxy s9?
Answer: From the Home screen, swipe up on an empty spot to open the Apps tray.
Tap Settings > Connections.
Tap the Bluetooth switch to turn on.
Tap Bluetooth. ... 
If your mobile device stops scanning before your Bluetooth device is ready, tap SCAN.
Tap the Bluetooth device in the AVAILABLE DEVICES list to pair with your phone.