Help to re pressurize Worcester 28i junior boiler

[davetro]

I have a Worcester 28i Junior boiler.
I need to re pressurise as the hot water only works when the central heating is on.

I know about the key underneath but no matter how I try I can't get it to fit in. There is a black nut to the right which I am supposed to turn and a white one to the left - but what happens now!!!! Confused!!!!!!! Have looked at technical stuff on the web and even more confused!!!!!

Please could you help - I need it explaining very simply!!! Much appreciated and thank you!!!!!

 

[ukrobj]

There are two keys for Worcester, one small, one large, if you have a large one and it won't fit, then your (wait for it) need the small one. Once you enter the filling key, turn it to the locked position and slowly open the white square next to the filling key till you reach 1bar.