When you arrive at the parking lot, please enter the code you were given when you made your reservation (QR code).
If you are unable to enter the parking lot, please take a parking ticket and go to reception with your booking confirmation. A member of staff will then give you a ticket which you can use on your way out.
The parking lot is covered and very convenient to get to the CDG Terminal 3 tram stop. I would recommend it, however, the instructions on how to enter and exit this parking are incomplete and wrong. They tell you that you need a code to enter and exit, but they never give you a code. After calling for help, you are told to take a ticket, enter the parking, and then when you leave, you need to talk to the reception to get a ticket to leave. The hotel staff was a little confused about all of this, and it is really unacceptable that you should have to deal with all this when trying to park your car before catching a flight. Though I spoke to everyone in french, I would imagine that this would be more confusing if you didn't speak french.
Over all the experience was good. The location is a little difficult to find. The instructions should provide a short video and like others I ended up taking a ticket rather than typing a code that is not provided in the email but referenced in the instructions. Once you do park it's very easy quick and easy to get to the airport. I'd give myself 30 min if it's your first time.