1. Open your terminal and enter "bluetoothctl" like here:
sk@susan:~$ bluetoothctl
Agent registered
2. Then enter "scan on" and press the button on the back side of your AirPods:
[bluetooth]# scan on
Discovery started
3. Then it will list the bluetooth controller and your devices:
[CHG] Controller XX:XX:XX:XX:XX:XX Discovering: yes
[NEW] Device XX:XX:XX:XX:XX:XX XX-XX-XX-XX-XX-XX
...
[NEW] Device 9C:XX:XX:XX:XX:XX Susanne’s AirPods
4. When finished you can connect to your AirPods:
[bluetooth]# trust 9C:XX:XX:XX:XX:XX
[bluetooth]# connect 9C:XX:XX:XX:XX:XX
Attempting to connect to 9C:XX:XX:XX:XX:XX
[CHG] Device 9C:XX:XX:XX:XX:XX Connected: yes
[CHG] Device 9C:XX:XX:XX:XX:XX Modalias: bluetooth:v004Cp510Fd602D
[CHG] Device 9C:XX:XX:XX:XX:XX UUIDs: 00000000-0000-0000-0000-000000000000
[CHG] Device 9C:XX:XX:XX:XX:XX UUIDs: 00000000-0000-0000-0000-000000000000
[CHG] Device 9C:XX:XX:XX:XX:XX UUIDs: 00000000-0000-0000-0000-000000000000
[CHG] Device 9C:XX:XX:XX:XX:XX UUIDs: 00000000-0000-0000-0000-000000000000
[CHG] Device 9C:XX:XX:XX:XX:XX UUIDs: 00000000-0000-0000-0000-000000000000
[CHG] Device 9C:XX:XX:XX:XX:XX UUIDs: 00000000-0000-0000-0000-000000000000
[CHG] Device 9C:XX:XX:XX:XX:XX UUIDs: 00000000-0000-0000-0000-000000000000
[CHG] Device 9C:XX:XX:XX:XX:XX ServicesResolved: yes
[CHG] Device 9C:XX:XX:XX:XX:XX Paired: yes
Connection successful