Copy content of a form in a web page to a new one

I've been asked by a friend to write a piece of code that can copy the content of a form in a web page to an other page (same form). it's basically a website where people sell all kinds of stuff and he wants me to write something that copies his previous ads, creates a new ones, paste the content there and validate so his ads are always on the first page.

i'm not quite sure how i can achieve this is there anyone here that can give some pointers?

Thank you