to make changes to the menu you will need to edit the webassist/plugins/main_menu/menu.php file.
the menu item you refer to is dynamicly genereted, you wont bbe able to change it, but you can add a link to the blog by editin this code:
<ul class="level-1">
<?php
echo($WACustomPages->Body);
?>
</ul>
to:
<ul class="level-1">
<li><a href="http:www.//rubiomonocoatonline.com/blog">blog</a></li>
<?php
echo($WACustomPages->Body);
?>
</ul>