Visit the Presidential Management Fellows (PMF) website to learn how you can become a PMF. Pay special attention to the PMF timeline.
Requirements for general eligibility, including graduation date and citizenship requirements can be found at

While the site advises this afternoon that the program is currently being updated, it also states that “The application period for 2012 is September 15-25, 2011” You will need to keep checking the site to see if that changes.
Not only is the window of application in September very brief, you must apply directly to the federal site and then immediately print out the form you receive from that site and present to the Graduate School (attn Judy Keenan) for review for school nomination. There is no possibility of any extension for application or nomination, and there is no way to obtain or submit a form outside the federal online system.
PMF competition is keen. Students nominated by their schools and selected for the next stage first take a federal test. Those who pass that test travel at their own expense to an in-person federal interview. Those who pass the interview (fewer than 10% of the initial nominees) become finalists. They are then allowed to apply to any agencies that might be hiring fellows. Finalists are not guaranteed any position–only an opportunity to apply. It is up to each agency to decide whether or not to hire.

Questions on the PMF program, eligibility or application requirements must be addressed to the contacts listed on the PMF web site.