The general outline of Mars Direct is simple. In the first year of implementation, an Earth Return Vehicle (ERV) is launched to Mars, arriving 6 months later. Upon landing, a rover is deployed that contains the reactors necessary to generate rocket fuel for the return trip. After 13 months, a fully-fueled return vehicle will be sitting on the surface of Mars.
During the next launch window, 26 months after the ERV was launched, two more craft are sent up: a second ERV and a habitat module (hab), the astronauts' ship. This time the ERV is sent on a low-power trajectory, designed to make it to Mars in 8 months -- so that it can be landed at the same site as the hab if the first ERV experiences any problems. Assuming that the first ERV works correctly, the second ERV is landed at a different site, thus opening up another area of Mars for exploration by the next crew.
After a year and a half on the Martian surface, the first crew returns to Earth, leaving behind the hab, the rovers associated with it, and any ongoing experiments conducted there. They land on Earth 6 months later to a hero's welcome, with the next hab/ERV already on the way to Mars.