The car parks open at Paris-Charles de Gaulle are:

The PAB car park  which provides access to terminals 2A. 
The PEF car park which provides access to terminals 2E and 2F
The PR car park which provides access to all of the terminals in CDGVal.

The Paris-Charles de Gaulle Subscription Office welcomes you Mondays, Tuesdays, Thursdays and Fridays from 8:30 to 12:30.

The car parks open at Paris-Orly are:

Parking P3 which provides access to Orly 1, Orly 2 and Orly 3.
The P4a, P4b and P4c car parks which give access to Orly 3 and Orly 4. 

Before access to the parking, check your departure hall (some companies may have been assigned to another terminal).

If you have a reservation in a closed car park, go to the car park associated with your terminal in the list above.