Display pages featured images in navigation

Hi, Im usind a travel demo imported to my Ocean WP and there is a beautiful main navigation, which have categories as main level pages. Whn you hover over them the dropdown menu opens with the latest posts of this category, showinf=d also the featured images of these latest posts. So I need to add to the menu a page with 3 subpages. And I want when hover over it, to display the dropdown menu the same way it is displayed for the posts, meaning with featured images! How can I do it?

Thank you!