Complex sentence: After two years aboard USS ARIZONA as her Number 4 Turret Officer, he was selected for training as a US Naval Aviator, graduating from Pensacola in 1937 and being designated Naval Aviator 5551; his orders were signed by Captain William F. Halsey.
Split into simpler sentences: After two years aboard the battleship "Arizona" as her Number 4 Turret Officer, he was selected for training as a naval aviator. Designated Naval Aviator 5551 upon graduating from Pensacola in 1937, his orders were signed by Captain William F. Halsey.