Paris from Denfert Rochereau by Metro...
So you have successfully arrived at Denfert Rochereau, now here's how to ride the Metro into Paris...
There are two metro lines you can take, line 4 in the direction of 'Porte de Clignancourt' or line 6 in the direction of 'Charles de Gaulle – Étoile'.
You can buy your ticket from the ticket office or from the ticket machines on the left as you enter the station if you have not pre-purchased it.
You can enter the Metro station via any of the gates in the station. As you can see there is 'push through' access hatch for larger luggage on the right and if you have something larger such as a push chair or wheelchair special access can be gained at the right of the entrance to trains in the other direction - but don't worry you will still get to the correct metro platform.
Your choice of line 4 in the direction of 'Porte de Clignancourt' or line 6 in the direction of 'Charles de Gaulle – Étoile' will depend on your final destination within Paris.
line 4 offers more options for onward travel, for example it will get you to Montparnasse, Gare de l'Est and Gare du Nord railway stations as well as the metro 'hub' at Chatalet in the heart of the city.
line 6 will also get you to Montparnasse plus this is the line if you are staying near the Trocadero or the Eiffel tower. For station options click on the line number to check destinations. You should do some research prior to you trip to familiarise yourself with the routes.
(It probably does not need saying but 'Charles de Gaulle - Etoile' is nowhere near Charles de Gaulle Airport - but just in case!)
To help plan your trip to your final destination check-out ratp's-interactive-map-here where you will find maps for RER trains, buses, night buses and the Metro.