Unless otherwise indicated, the code snippets you see below should be placed into your theme’s functions.php file.
Here is the code to reposition the primary navigation menu:
<?php
//* Do NOT include the opening php tag shown above. Copy the code shown below.
//* Reposition the primary navigation menu
remove_action( 'genesis_after_header', 'genesis_do_nav' );
add_action( 'genesis_before_header', 'genesis_do_nav' );