Complex sentence: Educated at Queen's College and Magdalen College, Oxford, he was elected in 1775 to a fellowship at Magdalen, of which in 1791 he became president for the next sixty-three years.
Split into simpler sentences: Educated at Queen's College and Magdalen College, Oxford, he was elected in 1775 to a fellowship at Magdalen. In 1791 he became Magdalen president, a post he held for the next sixty-three years.