From the speaker:
Switch on Beosound 2 3rd Gen.
Standing in front of the product, press and hold on the Bluetooth button for about two seconds to enable Bluetooth pairing. The light indicator will start flashing blue, and you get audible feedback. Your Beosound 2 3rd Gen is now ready to connect to your device (phone, computer, tablet, etc.).
Open the Bluetooth settings on your device and pair with the speaker.
From the Bang & Olufsen app:
Switch on Beosound 2 3rd Gen.
Open the Bang & Olufsen app, select Beosound 2 3rd Gen, go to "Product Settings", "Paired Bluetooth devices" and tap "Start Pairing".
Open the Bluetooth settings on your device and pair with the speaker.