WooCommerce Free Shipping based on user role

WooCommerce_free_shipping_user_role.php

<?php
function get_user_role() {
  global $current_user;

	$user_roles = $current_user->roles;
	$user_role = array_shift($user_roles);

	return $user_role;
}

add_filter( 'woocommerce_available_shipping_methods', 'woocommerce_unset_free_shipping_for_certain_users' );
function woocommerce_unset_free_shipping_for_certain_users( $methods ) {
	$user_role = get_user_role();
	if ( $user_role != 'administrator' )
		unset( $methods['free_shipping'] );
	return $methods;
}
?>

Where should i add this code? in functions.php?

Help with implementation.