Complex sentence: One of his instructors, the sculptor Louis T. Rebisso, encouraged him to try sculpting, and his first effort was a sculpture of a group of horses based on observations and drawings he had made at the U.S. Mail stables in Cincinnati.
Split into simpler sentences: One of his instructors, the sculptor Louis Rebisso, encouraged him to try sculpting. His first effort was a sculpture of a group of horses based on observations and drawings he had made at the U.S. Mail stables in Cincinnati.