When you have it on, make sure you have a stylus or your fingers on the Touch Screen at all times because that's how it works.
At first, you'll be hearing a continuous low ringing sound as you keep your fingers / stylus on the Touch Screen.
If the ringing slowly becomes louder and faster, you'll notice the machine screen starts slowly glowing. This means items are nearby.
As you get closer to the items, the screen glows even brighter, to the point of very bright yellow and the ringing is faster.
You'll eventually see dots / circles on the map as this happens, so plan your movements accordingly to what the machine displays.
If the dots / circles are in the middle of the machine (or very close to the middle), it means you are in front of the items and you can pick it up by pressing A.
Hope I helped! Source