These are musical mantras designed to help you focus your mind and take a rest from the compulsive chatter that fills your head every day.
All you have to do is focus on the drone and every time idea intrudes and takes your focus off the drone just make quick mental note of it and get back to the drone. Some of us find this difficult to do but that's OK. Just keep practicing.
One thing you can do is hum in unison with the pitch of the drone. That makes your body vibrate with the drone and become part of it. It can really help with keeping the focus on the drone.