Complex sentence: Upon the vessel's arrival at Whitehall, she was taken into the U.S. Navy and after being laid up, the vessel served as Commodore Macdonough's headquarters during the winter of 1814-15.
Split into simpler sentences: Upon the vessel's arrival at Whitehall, she was taken into the U.S. Navy. After being laid up, the vessel served as Commodore Macdonough's headquarters during the winter of 1814-15.