The Fly12 CE is an unsupported Fly device, check out our latest Fly12.
If a master reset is required, the reset button is located within the small cut-out as illustrated.
Carefully, using a fine object, press the reset button to perform the reset. You will know that this is done correctly as you will feel the reset button being depressed.

Warning: DO NOT complete a Master Reset when the unit is in the process of completing a firmware update as this may damage your Fly12 CE.