Went to Paris for 5 days.Booked a place over internet and paid by credit card.Got a receipt, printed out and shown afterwards in the reception. All went smooth,you can park before going through the barriers and shown the receipt.You'll get a pass for 5 days (or for how many you booked) and can get in and out as many times as you want. You need your pass to enter the parking from the street level via glass doors, than you go down 3 floors via a staircase. Nice access, easy to find, all good. Will use again.