How to add water pressure to this boiler? (with pics)

[bobiscuit]

I'm trying to bleed a radiator, but the air is trickling out far too slowly, so maybe I need to add pressure to the system?

The system is 2 years old, in a new-build house. I used to have a combi boiler with two taps underneath, very easy to add pressure - but I don't know how to do it with this new one.

There's a boiler unit in the garage that pretty much just has "ON" or "OFF", no other controls or gauges that I can see.
Then there's a storage tank thing in a cupboard upstairs, with lots of controls and I'm not sure what any of them do!

This is it. There's a single tap at the bottom (which was left in the wide open position by the installer... should it be?):

Close up of label:

The small red tank above the big white one, has a gauge currently reading 0 pressure.

Red controls:

If I turn any of the red controls slightly, I can hear water skooshing around. But even when I turn the one right underneath the pressure gauge, the pressure isn't affected. Although I didn't leave the red thing "open" very long... Do I just need to wait longer?

Any advice appreciated

 

[imiller9]

In your last picture, below the two red knobs is a silver flexible hose. At the bottom of it is a valve with a slot designed to fit a flat screwdriver. Using said screwdriver, turn the valve 90 degrees and you'll hear water entering the system. When the pressure gauge reaches 1 to 1.5, turn the valve off.

 

[zooankski]

IO would guess you need to open the fill line (braided hose) to top it up. Should be a valve at either end and it should not be left connected as shown. The red controls are temp and press relief valves.