Just faced this problem myself. This is how to do it.
Turn the boiler OFF at the mains switch.
The only valves that need to be touched are the black ones.
Open one fully and start to unscrew the second.
You will hear a hiss. This is the sytem filling. Speed of fill depends on how far you open the valve. Takes a minute or less. Watch the guage under the right front and turn off at 1.5 bar.
Turn both black valves to OFF and switch the boiler back on. Check the pressure after a while to make sure its stable. Job done.
Jim
January 2011