How can I edit or add products to my form?

I designed and have been using a form for over a year now, but I'm wanting to add another item to an element on the form and charge for it. I haven't been able to figure out how to add or even edit options within that element. Would love to have some help on this asap please. 

You could add, edit, remove or clone products by clicking on the payment field and on the wizard icon, there you will find such options. 

Here's also a screenshot as reference: 

If you have any question, let us know.