These are the instructions for the champ 4040 housing.
Remove the end cap from the feed end (the end with only one port) – this is achieved by pulling on the white tab which will remove the white holding ring. The end cap can now easily be removed. Remove the old membrane and clean out the housing. If you clean the housing with bleach then thoughly rinse it away with pure water from your van's tank, or water that has been through your sediment and chlorine block filters. Remove the new membrane from its packaging. Lubricate the centre shaft of the new membrane with a smear of silicone grease at each end. Insert the membrane into the housing with the black brine seal at the feed end (ie feed the membrane in with the brine seal end going in last). Push the membrane firmly to ensure it is fully inserted. Push in the end cap, again ensure it is fully inserted to reveal the holding ring groove. Replace the holding ring.