How to Hide WC China Checkout Admin Menus

function plt_hide_wc_china_checkout_menus() {
	//Hide the "WC China Checkout" menu.
	remove_menu_page('wc-sinic');
	//Hide the "WC China Checkout → Settings" menu.
	remove_submenu_page('wc-sinic', 'woo_ch_page_default');
}

add_action('admin_menu', 'plt_hide_wc_china_checkout_menus', 11);

Where do I put this code?