Fixed left sidebar

You can activate fixed position option to the left sidebar element by adding this class (am-fixed-sidebar) to the main wrapper (am-wrapper) element this way your main structure should be like this:

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