Complex sentence: Archbishop Rivas had been appointed Apostolic Administrator until the appointment of a new bishop and had appointed as his delegate Fr. Pio Atonio M.F., who oversaw the everyday running of the diocese.
Split into simpler sentences: Archbishop Rivas had been appointed Apostolic Administrator until the appointment of a new bishop. He has appointed as his apostolic delegate Fr. Pio Atonio M.F., who oversaw the everyday running of the diocese.