This is just a quick guide to changing a purge valve to a autoseal hose port.
First you must unscrew the purge valve cover, be careful not to drop the ball bearing.
Gently unscrew the bottom of the valve that is screwed into the stem. Go easy on the threads, you may need that purge valve again some time.
The screw the additional hose port into the same hole.
The autoseal port has a ball bearing in it so when you are smoking alone on the other port/hose the autoseal acts as a purge valve. The ball blocks the port when you inhale on the other side and then moves out of the way to purge when you blow into the other side. When someone is smoking on that side as well, when they inhale the ball lifts up and allows the smoke to travel up the hose.
The ports can be found here: