Worcester 28si boiler top up?

I have a very old worester 28si and the pressure is down to around 0.4 i cannot figure out how to up the pressure. The external filling hose doesnt seem to fit or do anything as it has one valve that i can turn halfway and the other one hasnt got a flathead screw fitting. There doesnt seem to be a internal filling kry eithet and im confused. Its in a little cupboard upstairs and underneath there is two connectors right next to it with another pipe running to a closed loop with a cap. There is a black turn valve on top of one that doesnt work either any suggestions. Just started livig on my own and this isnt my kind of area.