Why don't you take a look at the HTML generated? If you do not know how to make this kind of change you will need to educate yourself on HTML markup. This forum is not the place to learn CSS.

Well I see the is used for login form, but it is not listed in photos.css

So maybe you need to add it?

I take of this thread to ask if is it possible to integrate zenpage in this themes?

It is possible to integrate Zenpage into every theme. But we have no plans to do so.