I'm developing a classified script, I want that each member can register, upload your ads and view it in your personal area.
I create script for registration but I don't know how develop personal area, I think that I set 2 db: users and ads.

Personal area? what are they supposed to do in that area after logging in? Just to view their ads?
so then what happens to the ads that they have uploaded?

it might help us to help you once you answer the questions.

I want that they view and edit ads uploaded in your personal area.

You need to make use of sessions as phorce mentioned so you can check when registered users are logged in then they can upload ads and view/delete them. You need to make a log-in script and upload images/content script for ads.

What sort of ads are you gonna be storing in your DB? Are they image based or content based? Think about the size of images? By the way, what is the purpose of this project? Is this part of a big website because the problem you're trying to solve sounds a little small?