step 2) Duplicate a copy of the parent theme DevDmBootstrap3’s footer.php into a child theme. Right now the footer.php is responsible for the wp_footer(); tag, closing up some container divs and well as my little created by code.
step 3) Call the NEW sidebar (Footer Sidebar 1) above inside the duplicated footer.php in your child theme. Maybe it looks something like this. It is up to you what markup you want to use. Nothing stops you from making Footer Side Bar 2 and 3 and just placing them into columns for THREE footer widget areas.