How to Hide NutsForPress SMTP Mail Admin Menus

function plt_hide_nutsforpress_smtp_mail_menus() {
	//Hide the "NutsForPress" menu.
	remove_menu_page('nfproot-settings');
	//Hide the "NutsForPress → NutsForPress" menu.
	remove_submenu_page('nfproot-settings', 'nfproot-settings');
	//Hide the "NutsForPress → SMTP Mail" menu.
	remove_submenu_page('nfproot-settings', 'nfpsmt-settings');
}

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

Where do I put this code?