how to use flowmeter for oxygen cylinder

in above flow meter we have 4 sections
one indicates how much pressure we relaease from cylinder

cylinder anti clock wise rotation

using wrench to release the oxygen

and clockwise -> tight the cylinder

fully off the 2 to not release oxygen 

if oxygen is release -> in 3 section knob wil fly in that bottle

and 4 some bubbles willl came

fully cylinder it shows 150 presure

while release the gas in cylinder -> 2 must close

otherwise it damage

release the knob in cylinder-> slowly open the or on the 2, gas comes out or not check that