How to replace categories with menu?

Hey everyone.

I’m a novice, aspiring WordPress developer. I have a pretty basic understanding of HTML, CSS, and Javascript/JQuery. Starting to get my feet wet with WordPress development and PHP, but am very much so still a lost beginner. I’m trying to figure out how to make some changes to a site I’m editing using the Rock Music free theme. There is a menu of pages above the header slider, and a menu of categories below the header slider. I want the links from the pages menu to display where the categories menu displays beneath the header, and I want the pages menu above the header GONE. So basically, I want the links from the pages menu to display where the categories menu is instead of the categories links, and I don’t want any categories menu on the page at all. There’s no settings in my theme that make this achievable from what I can tell, so I’m guessing it’ll require some code hacking. Any help would me much appreciated!