Where is the modifications area for "post an ad"

Hi,

Since I am now deep in the forms module I figured I would find this area, but I have been through all of it I think and can't find it. I really thought it would be in forms - fields - ads - add ad, but it is not here. this is the page I am seeking to modify, it is originally in the add an ad post section

the publishing time thing is a cool option but doesnt work anywhere on my site so I want to remove it, 

and the location doesnt work so I need to just turn that into a text box they can type into, and I want to add some text to "header image" to explain what that is

Thanks!

:)