<nav class="navbar navbar-default" role="navigation">
  <!-- Brand and toggle get grouped for better mobile display -->
  <div class="navbar-header">
    <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#navbar-collapse-1">
      <span class="sr-only">Toggle navigation</span>
      <span class="icon-bar"></span>
      <span class="icon-bar"></span>
      <span class="icon-bar"></span>
    </button>
    <%= link_to "My Application", defined?(root_path) ? root_path : "#", class: "navbar-brand" %>
  </div>

  <!-- Collect the nav links, forms, and other content for toggling -->
  <div class="collapse navbar-collapse" id="navbar-collapse-1">
    <ul class="nav navbar-nav">
    </ul>
    <ul class="nav navbar-nav navbar-right">
      
    </ul>
  </div><!-- /.navbar-collapse -->
</nav>

<nav class="navbar navbar-default" role="navigation">
  <!-- Brand and toggle get grouped for better mobile display -->
  <div class="navbar-header">
    <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#navbar-collapse-1">
      <span class="sr-only">Toggle navigation</span>
      <span class="icon-bar"></span>
      <span class="icon-bar"></span>
      <span class="icon-bar"></span>
    </button>
    <%= link_to "My Application", defined?(root_path) ? root_path : "#", class: "navbar-brand" %>
  </div>

  <!-- Collect the nav links, forms, and other content for toggling -->
  <div class="collapse navbar-collapse" id="navbar-collapse-1">
    <ul class="nav navbar-nav"></ul>
    <ul class="nav navbar-nav navbar-right">
      <% if defined?(Devise) %>
        <% if admin_user_signed_in? %>
        <li>
          <%= link_to "Admin", admin_dashboard_path %>
        </li>
        <% end %>
      <% end %>
      <li>
        <%= link_to "Categories", categories_path %>
      </li>
      <li>
        <%= link_to "Products", products_path %>
      </li>
    </ul>
  </div><!-- /.navbar-collapse -->
</nav>

Add links to navigation bar
Add links to navigation bar
