How to Hide Notification Master Admin Menus

function plt_hide_notification_master_menus() {
	//Hide "Tools → Scheduled Actions".
	remove_submenu_page('tools.php', 'action-scheduler');

	//Hide "Notification Master".
	remove_menu_page('ntfm-home');
	//Hide "Notification Master → Home".
	remove_submenu_page('ntfm-home', 'ntfm-home');
	//Hide "Notification Master → Notifications".
	remove_submenu_page('ntfm-home', 'ntfm-notifications');
	//Hide "Notification Master → Settings".
	remove_submenu_page('ntfm-home', 'ntfm-settings');
	//Hide "Notification Master → Subscriptions".
	remove_submenu_page('ntfm-home', 'ntfm-webpush-subscriptions');
	//Hide "Notification Master → Notification Log".
	remove_submenu_page('ntfm-home', 'ntfm-notification-log');
	//Hide "Notification Master → Debug Log".
	remove_submenu_page('ntfm-home', 'ntfm-debug-log');
}

add_action('admin_menu', 'plt_hide_notification_master_menus', 11);
Where do I put this code?