how to turn on Navigation ?
 

I don't know why my forum don't display Navigation, so how to turn on it ?

http://123mypham.com/error.jpg

Those are the breadcrumbs and there is no option to turn them on or off. If they aren't showing, then you removed them from the navbar template.

I don't know why template navbar_link do not display although i edited it to see different.

<vb:if condition="$show['breadcrumb']">
<li class="navbit"><a href="{vb:raw nav_url}">{vb:raw nav_title}</a> 111</li>
<vb:else />
<li class="navbit lastnavbit"><span>{vb:raw nav_title}</span> 222</li>
</vb:if>

but 111 or 222 don't display

If your breadcrumbs are not showing, then modifying that template will not do any good since that modifies the breadcrumbs... which aren't showing.

Have you modified your navbar template and removed the breadcrumbs?