Your weldeig supply should have a Y with valves on 2 sides. Probably have to crank up the flow a bit and open the side going to the torch full and adjust the backflow down. The Y goes on the out side of the flowmeter. Your flowmeter may have left hand threads. I don't recall at the moment. They will know what fittings you will need if you know the flowmeter you have. Probably all the same.