When you arrive, head to the machine at the entrance.
To enter, scan the QR code indicated on your reservation. After a few seconds, once the QR code been read and recognized, the machine will issue an exit ticket. Be sure to keep it until the end of your stay at the car park, as you'll need it to get out. Next, the gate will open to let you enter. Park in any free spot.
If the gate doesn't open, use the intercom to get in touch with the car park operator: he/she will explain the next steps to follow.
To leave: use the ticket you got upon arrival. If you exceed your reservation time, the machine will ask you to pay the extra amount directly at the car park to be able to leave.
Lastly, you can arrive up to 10 minutes before the time indicated on your reservation for the QR code to be validated.
3, rue de la Chaussée d'Antin (depuis boulevard des Italiens)