@Patrick: If you want to center all the title of pages/posts then you can add the following css in “Appearance => Customize => Theme Options => Custom CSS Options” box:
.entry-header { text-align: center; }
But if you want to center only page title, then add the following css instead.
.type-page .entry-header { text-align: center; }
For Google Adsense above page title, I recommend you to search for plugin as it’s little complicated to do it from theme. To do it from theme, you need to build child theme, for child theme refer to http://catchthemes.com/blog/create-child-theme-wordpress/ and then add the code like below in your child theme functions.php file
function catchresponsive_adsense_above_pagetitle() { ?>
add in your code here
<?php
}
add_action( 'catchresponsive_before_page_container', 'catchresponsive_adsense_above_pagetitle', 20 );