First, make sure that the pulseaudio-module-bluetooth package is installed:
sudo apt-get install pulseaudio-module-bluetooth
and that the bluetooth service is running:
sudo systemctl status bluetooth.service
If it isn’t, start it:
sudo systemctl start bluetooth.service
The GUI will then open.
Enter pairing mode on this headset: Put the headset in both ears, then hold your fingers to the touch sensors on both the left and right units for about 7 seconds. You will hear voice guidance “Bluetooth pairing” from the left unit.
Click on the search button of blueman-manager and wait until your headset appears.
Then, right-click on “Connect”, and then right-click on “Couple”.
The final step would be to do the same thing with “Trust” if you want your headset to connect automatically, and to enable the bluetooth service at start:
sudo systemctl enable bluetooth.service