Public transportation :
Take the bus, métro or RER to the "Gare de Lyon" train station. You
will need to buy a train ticket at a "Banlieue" booth (or, if you have the appropriate change, at an automatic touch-screen ticket machine) for Fontainebleau/Avon. Then, follow the directions
given in the second and third parts of Section A.
More information: SNCF