Step 1. The inside of YM front plate.
  Step 2. Rotate the button "F" by 90 degree by screwdriver to become , observing the color in the hole (observing hole) changing from red to green, now the lock is in the code changeable condition
  Step 3.Rrotate the rotary buttons by 180 degree by screwdriver,when the red point adjoin to the symbol, it is part of the code, when the red point adjoin to "NO", it is not part of the code
  Step 4.rotate the button "F" by 90 degree, turn back to become ,the color in the observing hole turn to red, now the code has been confirmed.