Over filled my Ferroli boiler?

I recently had to repressure my boiler and add more water but had a problem getting the inlet pipe to close so over filled the boiler. The pressure gauge shows 3-3.5 when should be 1-1.5. The boiler is making noises through the night and I am getting a little worried that the over fill is causing this. The over flow is constantly running water and I would like to know how to drain some water off please. The manual I have is no use as doesn't touch on this problem.