This walkthrough will have two parts for each chapter: Story and Free Play, named after the two game modes. Story will guide you to the end, Free Play will guide you to studs. (for superkit pieces) For minikit pieces, see minikit piece locations Also, it'll assume you're playing as the first player, and the computer is playing as the second. However, it doesn't matter - just remember that the word "you" refers to the first player, and the words "the computer" refer to the second player.
You start in Dexter's diner. The first two characters that you have are Qui-Gon Jinn, and Obi-Wan Kenobi. In here, if you go over to where Dexter is, you find that you can buy characters, extras, hints, and use cheats. You can't buy anything, yet, as you have no money.
You can use the Force on the various objects in this room for money, (studs) but you can usually get them in the levels.
For now, just enter the door marked I, and enter the door in there marked 1.