On the date of your reservation, enter the parking lot as usual, take a ticket at the entrance and park in any empty spot.
Upon your return, drive your car to the exit barrier and call the intercom which is on the pillar of the barrier. A Quick operator will answer from the control room and ask you for information regarding your Parclick reservation. Afterwards, the operator will raise the barrier to allow you to exit the car park.
Piazza Nazionale