My father resigned in order to get a better position.
Literal
Father [topic-は] more good position [to-に] get [in order to-ために] resigned.
~ために expresses purpose: 'in order to.' 地位につく means 'to take/get a position.' 辞職する is a formal suru-verb for 'to resign,' built from 辞 (resign) + 職 (employment).