See image....
Some add a check valve to each line. They system will run fine without these. This system has check values in each line.
Connect up to your torch. Turn on the oxygen torch value and then start up the machines. After about 10 minutes (5 to 10) the oxygen purity should be up to specifications. Adjust the LPM flow value on each machine for a balanced reading. i.e. both at say 4.5 LPM, etc.
Enjoy the new machines!