Complex sentence: Having served as curate in Armagh City for a period, and then become Administrator of the Cathedral parish of Armagh, he was responsible for building the parish church of St Malachy's in that city.
Split into simpler sentences: Having served as curate in Armagh City for a period, he was then appointed as Administrator of the Cathedral parish of Armagh. He was responsible for building the parish church of St Malachy's in that city.