Conversation so far:
When did the first engines by James Watt come about?
In 1776
How did the engines work made by James Watt in 1776 work?
With Steam
Were the engines created by James Watt powered by steam a success?
the engine by James Watt was commercially successful, and for the next five years Watt was very busy installing more engines,
Did Matthew Boulton and James Watt keep making more engines?
These early engines were not manufactured by Boulton and Watt, but were made by others according to drawings made by Watt, who served in the role of consulting engineer.
Where were the engines designed by James Watt being installed?
mostly in Cornwall for pumping water out of mines

Question: How did he improve the engines over time?
Self-contained rewrite: How did James Watt improve the engines over time?