Hi Jonathan, First connect the pressure gauge to the equipment and purge the hose then connect the gas cylinder to the pressure gauge and also purge the hose then turn on the equipment with the high and low keys open and if the equipment is R22 you can place the gas in gas phase and you will not have problems but if the equipment is R410 you will have to take the liquid phase with the inverted cylinder and it is done by throwing small jets so that liquid gas does not reach the compressor. You place it until the return pipe becomes cold by perspiring but not frozen bone with ice. The R22 works at 60 -65psi and up to 70 if it is very hot and the R410 between 115 125 and up to 130 Psi if it is very hot