fixing peeled off paint

[seb500]

Hi all, I am in need of some help! As you can see by the title, some paint has peeled off underneath my passenger door and I'd like to fix it myself.

here is a picture of the culprit ->



I have bought some paint (primer and base coat) along with a pad to scrub off rust and some wet and dry paper to smooth it off.

I'm aiming to do this myself, but seeing as I have not done anything like this before I want to get some advice prior to it. How can I make it look as if nothing has ever happened?

Thanks!