wp-content/themes/yourtheme/functions.php
add the code like so after the bit of text that tells you where to add custom functions.
/*-----------------------------------------------------------------------------------*/
/* End Theme Load Functions - You can add custom functions below */
/*-----------------------------------------------------------------------------------*/
add_filter( 'woocommerce_product_tabs', 'sb_woo_move_description_tab', 98);
function sb_woo_move_description_tab($tabs) {
$tabs['description']['priority'] = 5;
$tabs['related']['priority'] = 10;
$tabs['reviews']['priority'] = 20;
return $tabs;
}
