How to re-pressurise Saunier Duval?

not sure what boiler i have but it is a Saunier Duval - at under my boil is a black tap i if i turn it the press screen gose up to what ever bar . The is also a red tap which is piped out this on mine boiler is how i can emply the boiler. I had my boiler fitter in 2008 brand new. It been one of the wost mistake i have made. Here in South East london non of the boiler guy would recoment it . and there desk are not very good. Info on the boiler is hard to fine, NEVER AGAIN WILL I WANT A Saunier Duval. Next time i will check out which mag to find out what good and not good.

Harjit london south east
May 2009