How to Hide Alex Reservations Admin Menus

function plt_hide_alex_reservations_menus() {
	//Hide "Reservations".
	remove_menu_page('admin-alex-reservations');
	//Hide "Reservations → Reservations".
	remove_submenu_page('admin-alex-reservations', 'admin-alex-reservations');
	//Hide "Reservations → Bookings".
	remove_submenu_page('admin-alex-reservations', 'admin-alex-reservations#/t/1/bookings/list');
	//Hide "Reservations → Customers".
	remove_submenu_page('admin-alex-reservations', 'admin-alex-reservations#/t/1/customers/list');
	//Hide "Reservations → Settings".
	remove_submenu_page('admin-alex-reservations', 'admin-alex-reservations#/t/1/app/settings/general');
	//Hide "Reservations → Support".
	remove_submenu_page('admin-alex-reservations', 'admin-alex-reservations#/app/support');
}

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