new code?

I have a Concept 6 Advanced Microprocessor control for my burglar alarm in my house, which has been there since it was built. Unfortunately the people who lived here before me don't seem to have left me the instruction manual. I would like to change the code from the one they used to one of my own but haven't a clue where to start. If anyone has any clue then please could you let me know....I don't want to upset the neighbours by setting the alarm off!!!!