How to Hide the "SPWPieChart" Admin Menu

function plt_hide_spw_pie_chart_menus() {
	//Hide the "Settings → SPWPieChart" menu.
	remove_submenu_page('options-general.php', 'spw-pie-chart-generator');
}

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

Where do I put this code?