Instructions
Unlock all the other doors. The first door, Episode I, is unlocked when you start the game. Completing the first level of Episode I, "Negotiations," will unlock the doors to Episodes II and III.
Complete all levels. Between them, Episodes I, II and III contain 17 missions to be completed. You don't have to perform exceptionally at these missions the first time you go through them; you just have to make it to the end of all 17 levels.
Achieve True Jedi status on all levels. This the hard step. One of the goals on each level is collecting "studs," small LEGO tokens that litter the area. Every time you collect studs, the Jedi Meter at the top of the screen will slowly increase. Collect enough studs on every level to fill the meter until it flashes. Once you have filled the Jedi Meter on a level, finish the level to save your progress. When you have achieved this goal on every stage, the fourth door will open and the True Jedi area will be available to you.