How do I decrease the pressure on a Falcon II boiler?

The pressure was on 1 but I was told that it should be between 1.5 - 2.

Adjusted the filling loop (not sure if this is what it was - silver bendy pipe) but the pressure went straight over to 3!! Tried turning the filling loop the opposite way but it made no difference. Slight leak underneath the red colour turning nozzle located under the boiler.