Gas boiler pressure around 0.4 (off), 0.8 (on)

Got the boiler serviced by Bord Gais a couple of weeks ago. I see in their T&C that pressurising the system isn't included in the service so that's annoying.
Anyway, obviously not using the heating a whole lot this time of the year so the first time I noticed a problem (rad's not heating) was a few days ago.
I'm in this house 6 years and have never pressurised the system (never even heard of it until searching for solutions this week).

There doesn't appear to be any taps or anywhere to fit a filling loop under the boiler. Reading up on it led me to a little black button like valve in the hot press. This valve would turn both directions when I first looked at it so didn't appear to be either on nor off!
I turned it probably 6 or 7 full rotations in either direction but as I wasn't sure what I was doing I put it back to near enough the position I started from.
Surely the valve should reach a point where it won't turn anymore so it is therefore off?
Is anti clockwise the right direction to "open" it?
I can't find anything that specifies how long it takes to pressurise, are we talking seconds or minutes?
I'd like to sort it out myself but am just a little bit wary because as I mentioned there doesn't appear to be any "on or off" position for the valve
and when I was fiddling with it during the week a drop or two of water came out, so would be concerned about not closing it properly and it ending up leaking.
Thanks

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You should get a local reliable gas service man who will give your boiler and system a proper service(unlike Bord Gais) who only give the boiler a quick safety check and will not touch the 'wet side' He will explain your system to you and show you properly how to make a water pressure adjustment and any other jobs which you can safely carry out yourself.

Your first picture shows an automatic air vent. This has nothing to do with pressurization. The black knob should be in a loose screwed position to keep it slightly open. It is not a critical setting.

Thanks bstop.
So I will go anti clockwise to build the pressure, then turn it back more or less all the way clockwise to close it?
Yeah, my main concern was leaving it open and building up too much pressure.

You may have a semi-sealed system which would be tank fed. There would be a gate valve with a non-return valve just below this. This would be located in the hot press.

I detest how BG & other similar so-called service companies work. A service is as per manufacturer's instructions in every case. All MI's state clearly that the expansion vessel pressure should be checked & the only way of doing this is to drain the boiler & check vessel pressure with no system pressure against it. So to say they do not touch the wet side is saying they do not service gas boilers as per manufacturer's instructions.

You may have a semi-sealed system which would be tank fed. There would be a gate valve with a non-return valve just below this. This would be located in the hot press.

What do i do in that case?

Open the valve to see if the pressure rises to 0.5 bar which is the minimum pressure most gas boilers will fire at.

Grand job, thanks Shane.
Will give that a go tonight.