You'll start the game with the first stage, Geonosian Arena. Release all three captives, slay the Nexu (the cat) by riding and charging it with the Reek (Rhino type animal). Next slay the Acklay (Spider type) by hacking it's legs, holding it with Padme's whip, and leaping on it with a Jedi.
Defeat Jango Fett next by throwing your lightsaber at him while he is flying. This will bring him to the ground for you to attack. He'll fly again. Do this three times to defeat him.
Finally open the three troop transport ships, wait for the the jedi to enter the transports, and close the doors behind them. After that, the stage is complete.