How do you use lighting on Star Wars Jedi knight 2 Jedi outcast

First you have to upgrade your powers, press ESC (exit) , then press "Player", then press Change Powers.. or something called like that... then wen you see a thing called :
........
Force: Light
........
change it to:
.......
Force: Dark
.......
You can see your points in the top of the power upgrades, Make sure you have enough points to upgrade your powers. Click 3 times on the "Lighting Power"
Then pres APPLY, and you will exit of the power upgrades, Press F5 close to an enemie and you will make you lighting power :), if you don't like F5 key press esc, Control, Secondary powers... or something related to that... Press Lighting and press ... for example key E instead of key F5 or key R instead of E or F5, The key closer to W,A,S,D... the better.