Usually, at the heating boiler, there is a junction for a hose with a valve and close by a pressure meter. If the pressure is too low, the janitor (not you) should fill up the heating system with water until the pressure is sufficient. Ideally, the pressure should be checked again after bleeding the radiators.
Exactly. That’s why either the janitor knows the correct pressure or they need to call a technician. Definitely not something to have hands on oneself in a building that’s not yours.