How to pressurise a Worcester 24i Junior

[maple129]

I have a worcester 24i junior that is 4 years old, the red light has been flashing for a while but I was able to press it and reset then it worked. but a few days ago, the red light came flashing again and would not stop. I know that it is because the water pressure is down to zero, as the black indicator mark is pointing to zero. But the boilder is fitted without a black manifold that is supposed to be used for refilling. Do anyone know how I can repressurie the boiler? There is a silver blaided flexible hose attached to some pipes that are feeding into the boiler, one end of the hose has a red knob (that is like a tap) and the other end with a little black thing on it. I have been searching the web for solution, but not quite sure whether that's what I need to turn to fix this. And do i need to turn off the boiler from the main switch when doing this? Somebody please help me! thanks so much

[AlBags]

No don't need to turn off.
You need to monitor gauge pressure while filling slowly.
The braided hose should be connected to a mains, then isolators in it to the boiler primary feed/return nearby, so pressure can be set in it.
You need to open one end of loop (if not open already) the slowly open other to let in mains pressure to charge.
You should not need more that 1 bar cold. I would set to that.
Then check bleed ALL the rads, and any air outlet bleed.
Then check/recharge again.

A water bylaw prohibits PERMANENT connection of systems to mains supplies. Hence the fill-loop (which is not regarded as "permanent"!