While playing the one player game, enter right,left,right,down,right,up while holding in the right thumbstick. You will hear a clarifacation sound. Go out into the main menu and level select will be on the bottom.
You will have the same character you used when you entered the code, and you will be able to use all secondary force abilities at full power. Core force abilitie levels depends on what level you choose.
Note: If you wanted to play the last level on the dark side from the selection menu, sorry, but it will always be the light side version. Also, if you turn the game off, you will have to enter the code again to get the level select option to come back.
A REALLY easy way to defeat Bobba Fett on the level where you have to blow up the weapon piles is to stay in the same position. Yes if you stay in the same position he will fire at you, you will deflect his shots, they will go flying back at him, easy.
WARNING you will take a teeny weeny itsy bitsy damage because you deflect them every time. I have completed this on the light side and i am going to do again but this time kill Rosh Penin when it is ok to. :-)