How can I increase the pressure in my Worcester Bosch greenstar junior? ?

I cannot figure out how to get behind the panel so that I can access whatever I need to access in order to increase the pressure. Currently the pressure is at zero and my showers are therefore hot for only a few seconds at a time.
Friends tell that 'all I need to do' is increase the water pressure as it should be about 1.5 bar. Surely this should be simple to do as it appears a common problem so I am nervous about taking my boiler apart in case there is a simpler solution. Please help!