How to add an input field in a delivery module in Zencart?

I was working on implementing the Royal Mail Airmail and DPD International delivery modules for a client. His website had been developed in Zencart and he wanted to use Royal Mail and DPD on his website. As there was no ready to use module available for these two so I got down to developing my … Read moreHow to add an input field in a delivery module in Zencart?