Flight
As the main international airport in France you will likely land there if you are flying from anywhere in USA (4h away from the Chateau by car) All the main American airlines (American, United, Delta Airlines) fly to Paris on a daily basis. Consider if you are flying from the DC area or NYC looking at Norwegian Airlines; this is a low cost company that will also take you to CDG.
Rental Car
You can rent a car at CDG directly when you land, the main car companies such as AVIS, Enterprise, Hertz, Sixt have a counter there. If you choose this option please consider booking the car on one of those companies website with the airport as the pickup and drop off place. Additionally make sure that you are renting an automatic car if you cannot drive a stick (this is the default option in France).
Train
You can take the train to Limoges, the biggest city close to the Chateau. Once you land at CDG you will have to make your way to Gare D’Austerlitz to take the train. You can take a taxi or Uber, but if you want to take public transportation please refer to the FAQ page to get more information on how to do so.
Rental Car
If you have elected to take the train from Paris to Limoges you can rent a car at the train station once you arrive to get to Coussac-Bonneval. Here again please ensure that you are renting a car that is automatic if you do not know how to drive a manual car.