TGV from Paris CDG

I am on my first solo adventure abroad and am flying into Paris CDG.  I have a ticket to take the TGV from CDG to Avignon. Is the TGV station actually in the airport or do I need to find a shuttle or something.  I want to make sure I have enough time to clear customs and catch my train. Any advice would be appreciated.                                                                                            Thanks                                                                                                                             Tom O'