Create a page template wich Custom Query (easy way : http://wpquerygenerator.com/) and then add this template to the page where you want to display 2 categories 🙂
I dont know how to do it .. can u do this for me ?
Do you have access to your FTP ? If so duplicate the page.php page on this server, follow those instructions to create a template : http://codex.wordpress.org/Page_Templates
And replace the content of the page with something like this
<?php
$custom_query = new WP_Query(array(
'cat' => '4, 6',
'posts_per_page' => 10,
'paged' => (get_query_var('paged')) ? get_query_var('paged') : 1
));
?>
(modify featured & home to the ID of your categories 🙂 Then you just have to create a page and choose the template you created from the right part of the edition area 🙂
Ideally you should be creating a child theme for these changes – not editing the main theme.