The membrane vessel has a cap at one end and a connection.  Remove the tube turn the cap to the left. The cap will come off and the old membrane will be visible. You can use pliers or some other tool to grab and pull on the plastic membrane product tube. Now you only need to pull for about an inch. After that inch the membrane will fly out if you keep pulling. Take the new membrane out of the bag, lubricate the o-rings at the end with water proof silicone lubricant. If you do not have any silicone, use some dish soap. The dish soap will make the o-rings slippery enough to install them correctly. Insert the membrane into the membrane vessel, make certain that it seats in the connection at the bottom. The membrane should fit just about flush with the end of the vessel, when correctly seated. Replace the cap and reconnect the tube. Now to the flow restrictor: The other end of the vessel has two connections. One waste the other pure water. Locate the waste water line follow it and see if you have a flow restriction device on it. If you find the device replace it with the new correctly sized flow restrictor. The arrow points to the drain. If you do not find one it is because the flow restrictor you have in inside of the drain tube. Remove the drain (waste) tube at the membrane housing and inspect it for a funky little piece of tubing and a small cap. Remove this in-line flow restrictor. Reconnect the tube to the membrane housing. Then install the new flow restrictor on the waste water line. Arrow pointing toward drain.