In the Settings screen there is a balance option. You can slide the silver dot right or left to set the desired amplification balance between left and right ears.
This setting is applied to the volume control, in addition to the results of the built-in hearing assessment, and will be active in all operation modes of the headset: phone calls, audio playback and personal hearing amplification.
For more information, use this link to see the video instructions, or this link to read the manual.