It is all pretty simple. Basically, a regular boiler will take water from the tank to provide heating. It is important to place your tank as high as possible to have a better water flow in all the system.
A heat exchanger warms up the cold water once you turn on the hot tap or switch on the heating. After that the hot water moves to the hot water storage cylinder where it is kept and circulated. Then valves will direct hot water to the heating system or the taps and outlets.