The theme supports one (1) menu which is responsible for making the pages appear as tabs on your home page right below the categories (e.g. Home, Contact Us, etc.)
If the pages do not appear, go to Menus under Appearance. You should see an option at the left hand side of the page that says "Theme Locations". Make sure that you have the menu like the "Home Page Nav" active. You can click the drop down and choose the appropriate menu and hit save.
If you have all the other Pages appearing except for a New Page you just added, in the same section look for the title of the page you created under the "Pages" section and tick the box to select it. Then click on "Add Menu" to include it to your current menu option. You will then see it added to the list of pages on the current menu. Don't forget to click "Save Menu" to completed the process. The new page should now appear as tab on the home page.