Boxed layout

You can activate boxed layout option to the main content by adding this class (be-boxed-layout) to the main wrapper (be-wrapper) element, and adding the class (be-alt-bg) to the body element, this way your main structure should be like this:

<html lang="en">
  <body class="be-alt-bg">
    <div class="be-wrapper be-boxed-layout">
      <nav class="navbar navbar-default navbar-fixed-top be-top-header">
        <!-- Top bar -->
      </nav>
      <div class="be-left-sidebar">
        <!-- Left sidebar -->
      </div>
      <div class="be-content">
        <!-- Main content -->
      </div>
      <div class="be-right-sidebar">
        <!-- Right sidebar -->
      </div>
    </div> 
  </body>
</html>