app/views/layouts/admin.html.erb

<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <title>Barong Admin</title>
    <%= csrf_meta_tags %>
    <%= stylesheet_link_tag    'admin', media: 'all' %>
    <%= stylesheet_link_tag @styles unless @styles.nil? %>
    <%= javascript_include_tag 'admin' %>
  </head>
  <body>
    <%= render 'admin/shared/navigation' %>
    <%= yield %>
  </body>
</html>