It's quite simple to open the entry or exit of a location with a presence sensor. All you have to do is:
Stop your vehicle on top of the underground sensor.
Only then tap 'Open Entry' on your access page.
Wait for the gate to open and drive in/out.
This is how you can identify the presence sensor on the ground:
It can happen that a location doesn't have clear markings on the ground, showing where the presence sensor is. In this case, stop your vehicle next to ParkBee signage as you see here: