Fontainebleau

I have questions on how to get to Fountainebleau from Paris. I tried to look up the train schedule and it said there were no trains to Fountainebleau on the day I had chosen, a Monday. Then I read further in an old Lonely Planet France guidebook and it says you can only buy tickets at the Paris Gare de Lyon SNCF counter or machines there at the station. If anyone has had experience with this, please let me know. The guidebook also says there are up to 40 trains a day on that route, so my assumption is there will be plenty to choose from. It also says you can take a bus to the actual Chateau. Thank you in advance!