How do I increase the system power to between 1 and 1.5?

I have a Sime Murelle HE 30 BF Code 8106312 installed March 09.
Today it shows the red light and ALL 02 with 1.1bar.
I have tried to put it right using the User instructions booklet.
Page 7 states 'To proceed increase the system pressure to between 1 and 1.5 bar.'
However, it does not give any instruction as to how to do this! I have scanned and scanned the booklet for this information. Surely there should be some further instruction/information as it does not say that I need to 'seek help and advice from a qualified engineer' for an ALL 02 situation.

I find it very baffling! Could you please help?

Many thanks