How to Hide wpOpus - The Ultimate Gutenberg Toolkit and Site Builder Admin Menus

function plt_hide_wpopus_menus() {
	//Hide the "wpOpus" menu.
	remove_menu_page('wpopus');
	//Hide the "wpOpus → wpOpus" menu.
	remove_submenu_page('wpopus', 'wpopus');
	//Hide the "wpOpus → Demo Import" menu.
	remove_submenu_page('wpopus', 'wpopus-demo');
}

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

Where do I put this code?