Add dropdown menus with a little extra HTML and the dropdowns JavaScript plugin.
<ul class="nav nav-tabs">
<li>
<a href="#">Home</a>
</li>
<li class="dropdown">
<a href="#" class="dropdown-toggle" data-toggle="dropdown">Dropdowns <i class="fa fa-caret-down"></i></a>
<ul class="dropdown-menu">
<li>
<a href="#" tabindex="-1">Item</a>
</li>
<li>
<a href="#" tabindex="-1">Item 2</a>
</li>
</ul>
</li>
</ul>