Unless otherwise indicated, the code snippets you see below should be placed into your theme’s functions.php file.
Here is the code needed to customize the next (newer) page link:
<?php
//* Do NOT include the opening php tag shown above. Copy the code shown below.
//* Customize the next page link
add_filter ( 'genesis_next_link_text' , 'sp_next_page_link' );
function sp_next_page_link ( $text ) {
return 'Custom Next Page Link »';
}