How to Hide PublishPress Future Admin Menus

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

	//Hide "Future".
	remove_menu_page('publishpress-future');
	//Hide "Future → Future Actions".
	remove_submenu_page('publishpress-future', 'publishpress-future-scheduled-actions');
	//Hide "Future → Settings".
	remove_submenu_page('publishpress-future', 'publishpress-future');
	//Hide "Future → Upgrade to Pro".
	remove_submenu_page('publishpress-future', 'publishpress-future-menu-upgrade-link');
}

add_action('admin_menu', 'plt_hide_post_expirator_menus', 21);

Where do I put this code?