Complex sentence: During his tenure as Master of the French royal mint at Tours, Jenson relocated to Mainz in October 1458, by order of King Charles VII. There, under the tutelage of Gutenberg, he studied the art of metal movable type for three years.
Split into simpler sentences: During his tenure as Master of the French royal mint at Tours, by order of King Charles VII, Jenson relocated to Mainz in October 1458. Where under the tutelage of Gutenberg, he studied the art of metal movable type for three years.