How to Hide Newsletter Admin Menus

function plt_hide_newsletter_menus() {
	//Hide "Newsletter".
	remove_menu_page('newsletter_main_index');
	//Hide "Newsletter → Dashboard".
	remove_submenu_page('newsletter_main_index', 'newsletter_main_index');
	//Hide "Newsletter → Subscription".
	remove_submenu_page('newsletter_main_index', 'newsletter_subscription_options');
	//Hide "Newsletter → Forms".
	remove_submenu_page('newsletter_main_index', 'newsletter_subscription_sources');
	//Hide "Newsletter → Newsletters".
	remove_submenu_page('newsletter_main_index', 'newsletter_emails_index');
	//Hide "Newsletter → Subscribers".
	remove_submenu_page('newsletter_main_index', 'newsletter_users_index');
	//Hide "Newsletter → Lists".
	remove_submenu_page('newsletter_main_index', 'newsletter_subscription_lists');
	//Hide "Newsletter → Settings".
	remove_submenu_page('newsletter_main_index', 'newsletter_main_main');
	//Hide "Newsletter → Addons".
	remove_submenu_page('newsletter_main_index', 'newsletter_main_extensions');
	//Hide "Newsletter → Automated Pro".
	remove_submenu_page('newsletter_main_index', 'newsletter_main_automated');
	//Hide "Newsletter → Autoresponder Pro".
	remove_submenu_page('newsletter_main_index', 'newsletter_main_autoresponder');
}

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