WooCommerce Custom Orderby

gistfile1.php

<?php
add_filter( 'woocommerce_get_catalog_ordering_args', 'custom_woocommerce_get_catalog_ordering_args' ); 
function custom_woocommerce_get_catalog_ordering_args( $args ) {
  if( isset ( $_SESSION['orderby'] ) ) {
  	switch ( $_SESSION['orderby'] ) {
			case 'sku_asc' :
				$args['orderby'] = 'meta_value';
				$args['order'] = 'asc';
				$args['meta_key'] = '_sku';
			break;
		}
	}
	return $args;
}
 
add_filter('woocommerce_catalog_orderby', 'custom_woocommerce_catalog_orderby');
function custom_woocommerce_catalog_orderby( $sortby ) {
	$sortby['sku_asc'] = 'SKU';
	return $sortby;
}
?>

Good morning, thanks for the input, I'm new to this and am learning, my question is if this code snippet is used to sort the products in my shop WooCommerce according sku, and if so what should I do? Where shall I put it? Thank you very much in advance and sorry for my English.

alias: it goes in your themes functions.php. Google "theme functions.php" and you'll see walkthroughs of how to paste code.