Nation is a theme base on DrupalExp theme, so it provide a complete layout builder which allows you to manage the page layout of site using simple drag and drop elements without coding. You can specify order of sections and regions, the size of individual blocks regions, move regions to any position of page or disable them. You also can create multiple layouts and assign to pages.
On Theme settings page (http://yoursite.com/admin/appearance/settings/nation) click on Layout settings tab on left sidebar
For more detail about layout here: https://docs.drupalexp.com/drupalexp-framework