How to Hide the "WP Mini Menu" Admin Menu

function plt_hide_z_mini_admin_menu_menus() {
	//Hide the "Settings → WP Mini Menu" menu.
	remove_submenu_page('options-general.php', 'z_mini_menu_plugin');
}

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

Where do I put this code?