How do you use the sensitivity dial in the National Geographic Kids metal detector?

Do you own it, if so how are you supposed to raise the volume or beeping sound. I dont understand the part from these instrunctions :Locate the sensitivity dial. Using your thumb, turn the dial on the directon marked ON. The Red power light will illuminate... My problem is, my detctor doesnt have an "on" thing and BOTH THE RED AND GREEN illuminate . Is it supposed to do that? Help me!! THNX!!!How do you use the sensitivity dial in the National Geographic Kids metal detector?
The metal detector must have an on/off switch somewhere or you'd have to remove the batteries to keep them from being used up between uses. But that's not important to setting the sensitivity control. Usually, you would make sure the unit is on then hold it at the recommended distance from the ground. Turn the sensitivity dial until the metal indication just shuts off or beeps very slowly. Then when you go over some metal the unit should beep at a faster rate. You can test the operation by putting some metal, a coin works fine, under a rock and see if the detector finds it. Keep adjusting the sensitivity dial until it indicates the coin is there and doesn't indicate the coin when you remove it and check again.