This is how to add a new button linking either to a page, blog category or external link to the top navigation menu as pictured below.
1. Create a page
(Pages-> Add new)
2. Go Here
(Appearance->Menus)
3. Locate your newly created page checkbox within the ‘Pages’ box, check it and click ‘Add to menu’. Click Save Menu.
4. The order of buttons can be adjusted by dragging and dropping the menu items within ‘submenu’.
‘Custom Links’ allow you to define your own URL for a menu button, these can be external.