The train takes you to Antony station which is the terminus for the OrlyVal on the RER line B. You need to transfer to another train to get into central Paris. Your ticket for the journey should costs around €10.00. Your ticket will be valid on the Orlyval train, the RER, and the Métro.
Trains are from 6 a.m. until 11 p.m and the journey time into central Paris should be around 40 mins.
Tickets can be bought at the RATP booth in the terminal, then take the escalator to the train station. Keep your ticket with you throughout the journey. It will be needed for the turnstiles at Antony and to exit the RER.
For your return journey, you can buy a ticket through to Orly at any RER or Métro station.
If you are staying in Paris prior to visiting the Loire Valley you might want to consider a visit to Disneyland Paris, Click here for information on Disneyland Paris