how do i set a switchmaster 300?

I have a switchmaster 300 boiler that controls the heating and hotwater in the house.
when i want to shower,i turn the switch to the ON position and heat the water for 2hours before showering.
it has a timer and i would love to know how i can set it to switch on/off automatically without me doing it manually.
this will help me have both the heating and hot water on simultaneously.