You have a hot water output pipe and cold return on the boiler. does
the pump run? The fill valve-valves should be on the boiler return
going to city supply. I would not just turn it on and leave it since you
could overfill it fast if your system is small, at 35lb your pressure
relief would open, you don`t realy want to get above 8-10 cold to start.
I run 12-15 on a boiler in a basement of a 3 story, less hight you need
less pressure. You only want enough water in it to get all the air out
and heat radiatore evenly when hot. I have never blead a system
cold,[but try it], and not running since pressure builds as the boiler
heats.