Refrigerant

Refrigerant in cylinder is in liquid-gas equilibrium state with certain pressure depending on ambient temp. Always liquid is charged keeping cylinder valve downwards (or hanging it upside down) to evaporator in the system (because it will be at lower pressure compared to cylinder). Ensure leakproof connection.

the gas cylinder is fitted in the inlet line of the compressor suction, where the angle valve or some sort of different fitting is given to fix your gas cylinder with the help of tube.

after that cooling system, like condenser with cooling tower or any other cooling system in the refrigeration plant is started

after that compressor started which will suck the gas from gas cylinder via inlet and then send to condenser, where the gas will cool.

after achieving the desired pressure compressor is stopped and cylinder disconnected