In the book Les Miserables how do Cosette and Jean Valjean get into the French Revolution?

PLEASE HELP It's not even about the French Revolution...>_>;; It's the student revolution...the story took place roughly around 1804, and Cosette and Marius hardly even were mentioned until 1832 -- the year General Lemarque (revolutionist, you know him?) died. The French Revolution ended 1799. :D