How do the steam turbines work and how can I start them?

In steam turbines, the pressure energy is converted into kinetic energy across the turbine blades.
This drop in pressure of steam rotates the turbine rotor and power is transmitted through shaft to the load e.g., pump, generator etc.
Turbine start up is a long story.......

The steam turbine worked on rankine cycle while the gas turbine on bryton cycle.

Rankine cycle: The Rankine cycle is an idealised thermodynamic cycle of a heat engine that converts heat into mechanical work. The heat is supplied externally to a closed loop, which usually uses water as the working fluid