How do I lower the pressure in my Fer Falcon combi boiler?

I have a Fer Falcon 0003L60333. It crashed and gave me freezing cold water while the shower was in use! I reset the thing but prior to that the bar level had dropped to below 1. I put some water in using the cold water inlet valve and managed to turn it back on, once I realised I had to reset the timer!!
When I put the heating back on the bar needle passed 3 and a half and the boiler was making some funny noises. I checked the overflow but nothing appeared to be coming out...as I had expected. I turned off the heating and now we are all freezing. I know there is a series of levers under the boiler but do any of them lower the bar pressure? Please help.