Becasue of cheating, single player has been disabled. Play on battle.net.
You can choose what Side you are on. The Dark side focuses on killing, the Light on healing, protecting.
After you fight your way to either the Jedi Temple (left) or the Dark Side Academy (right) you then make your way to Clearloft city. Where you have found out that an enemy has captured 16 Dark and Light Jedi Masters.
The Jedi realize this problem. And that they must combine the Light and Dark Sides. It is the only way to destroy this new enemy. Make your way to River City to assemble and army to fight the new danger to the Galaxy.