Underneath the boiler (right hand side) there are two black knobs, both move 1/4 turn. The knob closet to the front pushes away, the knob towards the back (attached to the PRV) pull towards you. Open them both, carefully watch the pressure on the dial until it reaches 1-1.5 bar (green area on the dial), then turn them both back off.
Carefree, October 2011