This is an inevitable Achievement that you will obtain by playing through Story Mode. Simply complete all six levels in Episode III: Revenge of the Sith that are listed below to earn the Achievement.
Chapter 1 - Battle Over Coruscant
Chapter 2 - Chancellor in Peril
Chapter 3 - General Grievous
Chapter 4 - Defense of Kashyyyk
Chapter 5 - Ruin of the Jedi
Chapter 6 - Darth Vader