Re: How do I build a module / addon?
This will depend entirely on what it is you're trying to integrate into Zen-Cart. Different modules/add-ons use different files. Is it something that can also stand alone, or will it be exclusively for Zen-Cart? Payment or Shipping module?........other module/add-on?
See, right now, we don't know how to help you, as we don't have a clue as to what you're trying to do.
With a few more details, we could maybe understand what you're trying to accomplish AND be able to better advise/help you.
Teach them to shop and they will shop today;
Teach them to Zen and they will OWN a shop tomorrow!