What did James Watt put to make the steam engine to work?

James Watt improved the steam engine by adding a separate condenser, which allowed steam to be condensed without cooling the cylinder. This innovation significantly increased efficiency by preventing heat loss and minimizing the need for the engine to cool down after each cycle. Additionally, Watt introduced a rotary motion mechanism, enabling the steam engine to perform various tasks beyond pumping water. His enhancements were crucial in advancing the industrial revolution.