Steps to change installer code on Networx NX-4

Hi DIY'ers, Apologies if this question has already been answered. I did do a search of the forums and couldn't find steps for achieving this. I have a Networx NX-4 security system, of which I know the current installer code. What I want to know is how to reset the installer code to something unique (As it is currently the factory default, meaning a serious vulnerability for undesired visitors) Any help would be greatly appreciated Many Thanks