Just a simple form feed add

I want to add two form fields on a project done on code igniter, the fields are Expiration date and expiration date alert< one field is to record the product expiration date and the other field is to send alert on a date when you need to be notified that the product would soon expire

here is a link to the actual software

https://codecanyon.net/item/stock-manager-advance-with-point-of-sale-module/5403161

i just need someone who can add the two specified fields to the add product page