From Paris-Charles de Gaulle airport:
You can take taxis from Charles de Gaulle airport to the exhibition centre (10 mn drive).
Take line B of the RER in the direction of "Robinson-Saint Rémy les Chevreuse" and get off at the first station: "Parc des Expositions".
From Orly airport:
Take the Orlyval to "Antony" station, then line B of the RER in the direction of "Aéroport Charles de Gaulle". Get off at the "Parc des Expositions" station.