How can i add tabs?

By default Lithium components don't come with a "hide/reveal" functionality built in. So you would have to create a custom widget that does some JavaScript magic. But then you can simply include the stock Lithium component within the container. No need to recode these.

Create a custom component and include the builtin components like this (or your own). You can then use JS / CSS for the tab view

<ul>
<li>
<@component id="forums.widget.recent-threads"/>
</li>
<li>
...
</li>
</ul>