How to Hide WP-ISPConfig Admin Menus

function plt_hide_wp_ispconfig_menus() {
	//Hide "WP-ISPConfig".
	remove_menu_page('ispconfig_dashboard');
	//Hide "WP-ISPConfig → WP-ISPConfig".
	remove_submenu_page('ispconfig_dashboard', 'ispconfig_dashboard');
	//Hide "WP-ISPConfig → Settings".
	remove_submenu_page('ispconfig_dashboard', 'ispconfig_settings');
	//Hide "WP-ISPConfig → New Website".
	remove_submenu_page('ispconfig_dashboard', 'wpispconfig_new_website');
	//Hide "WP-ISPConfig → Domain Alias".
	remove_submenu_page('ispconfig_dashboard', 'wpispconfig_domain_alias');
}

add_action('admin_menu', 'plt_hide_wp_ispconfig_menus', 16);

Where do I put this code?