picture in slider

Hi all,
I installed your beautyful theme, everything is ok, but… the image.
Both in the upper slider for the highlighted category and in the thumbnails below I see title and content ut no image.
I tried and change position to my attached pictures inside posts, and some other way, but nothing changed.
I didn’t see theme option about it.
Coul you please explain how can I obtain the same look that the theme has in demo?
thank you very much