How does a steam engine do work?
(a) steam turns a turbine.
(b) steam enters a cylinder and pushes a piston.
(c) steam expands and spins an axle.
(d) steam causes wheels to turn.

As water is heated up, it turns to steam

steam expands and enters a cylinder

a piston is pushed by the expanding steam in the cylinder
this action is the steam doing work on the piston

the motion of the piston is translated into a rotation motion, which can then be used to drive stuff