How to Hide Caxton Admin Menus

function plt_hide_caxton_menus() {
	//Hide the "Caxton" menu.
	remove_menu_page('caxton');
	//Hide the "Caxton → Caxton" menu.
	remove_submenu_page('caxton', 'caxton');
	//Hide the "Caxton → Contact Us" menu.
	remove_submenu_page('caxton', 'caxton-contact');
}

add_action('admin_menu', 'plt_hide_caxton_menus', 1000000000);

Where do I put this code?