Very simple to do. While the machine is on, select the down button to enter into the "setting" mode. Then scroll to the Microphone option with the down/up button and select by pressing the "Ok" button. Then you get the option to turn On or Off the microphone.
I highly recommend the microphone setting to be ON at all time if your intention is to record evidence of your driving and of others. The microphone can also work as evidence whenever you get pulled over and you use it in court, you will have video and voice recorded evidence. In an incident/accident, the voice recording will add more value to your evidence (or the opposite if it is your fault, which you may delete). The microphone feature in this device is the feature that made me purchase this PAPAGO!
One of the main reasons for all dash cams is to have proof/evidence and this will work well you don't have a witness that view the incident.
Images for this Answer
(click to see full-size image)