If your boiler pressure is too high, you’ll need to bleed water from the system.
Oil boiler bleeding instructions for reducing pressure
1. Locate the drain cock or a radiator bleed valve.
2. Loosen the valve slightly to allow water to escape slowly. Do this until the pressure reaches the recommended level. It’s much easier if you have someone helping you as one person can release water while the other monitors the pressure reading on the boiler.
If the pressure is too low, you’ll need to add more water to the system. You can do this by opening the valve on the external filling loop, which is usually located below the boiler casing. Your instruction manual should explain the process.