By default the header will have an hamburger icon which needs to be clicked to open the menu.
After clicking the Menu button the menu will open on a white background.
By adding the class header-open your menu will be shown on page load.
Add the class header-transparent and your menu won't have a background.
By default the footer has the light grey background and is centered
Choose a dark footer by just adding the class "footer-dark text-light" to the footer tag
<footer class="footer-dark text-light">
You can easily switch to a column layout by using the column shortcode