Difficulty applying new posts in the categories on feature

Kind of an odd question. I’ve got a menu bar that lists seven different categories, but on worpress these come up as “pages.” I’m having difficulty creating sub-posts under these pages. Anytime I create a new page with the proper parent page, it doesn’t publish. I’ve also installed the featured content gallery in hopes of having the ability to click on the front page to take you into the site. All this has done so far is refresh the front page. I couldn’t be happier with my wordpress appliciation. I just need some further assistance in making this blog a success!!!

Thanks!