How to increase water pressure in SIME format 34 boiler?

I have a SIME format 34e boiler and water pressure drops to zero. I cannot identify the right pipe to fill water for increasing the pressure. Any one has idea how to fix this problem?
Zhian, July 2017


done
Its one thing to repressurise but why did the pressure drop in the first place? You may have a leak somewhere or a weeping pressure relief valve

acp, July 2017
Why not search online for a manual?

Acp, July 2017
link Click here to see other fixes for Sime.