VUW PL 200 / 2-5 Vaillant combi boiler - how to increase water pressure?

Combined boiler, VUW PL 200 / 2-5 Vaillant.
Where is the valve that I can use to pump water into the installation? I have 0.5 bar. Photo attached:

In the picture I have marked the valve for filling the installation in red, thanks to which you will increase the pressure on the boiler.

Just use a flat screwdriver large enough to not chip the screw.

Erbit wrote:

Water is allowed "for installation" and not "for boiler".

Indirectly, by filling the installation, the pressure on the boiler increases, so from an amateur point of view it does not matter what it will be called

Erbit wrote:

For me it is solved differently and I had no idea that there could be such a valve at the boiler

I have a similar boiler, but 24kW, so I know this design very well, so solving the problem was very easy for me.
If you do not know this patent, you might think that there is nothing there. The installation is powered by a small pipe, which can be seen in the second picture just below the WILO pump, which connects the filling valve with the return pipe, which I don't know if I read the photo correctly, but here I think the filling valve itself, because I have a version with a check valve, i.e. I have an additional protection against mixing contaminated (CH) water with clean (tap) water.