There are many ways to get Joint Professional Military Education I (JPME I). You can do it on-line, via CD-ROM, by attending a war/service college full-time (cheat sheet here), or by attending a distance learning program where you live. This last option, run by the Naval War College, is called the Fleet Seminar Program.
In brief, you attend class once/week from September to May. Once you are done with all three courses, you have JPME I. And if you complete 9 additional credits in a concentration area you can get a Masters degree from the War College without ever having to attend it full-time.
Here is the application information: