Players that are not Sith trained use Force Powers as listed in the book and Morality as listed in the book, this includes those that started as Sith and have now turned to the path of Jedi. So if you roll Force Dice to fuel your powers and you roll Dark side pips you have to spend Destiny to use them and suffer strain equal the Dark side pips you use and also Conflict in the same amount.
Sith trained utilize the Dark side, and suffer strain when using the Light side if they spend Destiny to use and also Conflict just normal users would but when using Light side pips. Sith Morality is reversed so rising Morality brings them closer to the Dark Side and going lower brings them closer to the Light.