To clock in or out, just touch your iButton to the appropriate iButton probe. You’ll hear a "beep" and the light in the probe will flash.
The metal part of the iButton must touch both the inner flat surface of the probe as well as the inner rim of the collar.
If you touch your iButton to the probe and nothing happens, hold the iButton gently against the probe and slide the iButton slightly to the side, so the iButton makes contact with the rim of the probe.