Adding Extras to an existing order?

[Guest beccadex]

So I’ve been using fiverr for a little over 2 years now, and while I am strictly a seller, I’ve come across instances where my buyers will ask me how to do certain things that I cant really answer because I’ve never bought a gig, i simply dont know how they work.

If someone could give me a quick rundown of how to Add an extra to an existing order {such as an HD option to a video]