Go to Cour St Emilion metro station by the hotel. Bring cash. Go to ticket vending machine and buy fare to CDG airport with desired terminal selected. Get on line 14 direction St Lazare. Get off at Chatelet. Connect to RER line B to CDG using the same ticket. Keep ticket all the way to the end of the journey. There are several RER B's so ask at the station and get on the right one. Keep an eye on your stuff and be ready for a cozy ride. Did this recently with no problem. Allow plenty of time. I believe transit time is almost an hour.
The train is busy. Cost in the vicinity of 9€. Hope this helps and good luck.