Tips on Customizing Paytium: Mollie payment forms & donations

How to Hide Paytium Admin Menus

function plt_hide_paytium_menus() {
	//Hide "Paytium".
	remove_menu_page('paytium');
	//Hide "Paytium → Payments".
	remove_submenu_page('paytium', 'edit.php?post_type=pt_payment');
	//Hide "Paytium → Settings".
	remove_submenu_page('paytium', 'paytium');
	//Hide "Paytium → Setup wizard".
	remove_submenu_page('paytium', 'pt-setup-wizard');
	//Hide "Paytium → Extra features".
	remove_submenu_page('paytium', 'pt-extensions');
	//Hide "Paytium → Pro versions".
	remove_submenu_page('paytium', 'https://www.paytium.nl/prijzen/');
}

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

Where do I put this code?

How to Hide Paytium Meta Boxes

function plt_hide_paytium_metaboxes() {
	$screen = get_current_screen();
	if ( !$screen ) {
		return;
	}

	//Hide the "Payment details" meta box.
	remove_meta_box('pt_payment_details', $screen->id, 'normal');
	//Hide the "Subscription first payment" meta box.
	remove_meta_box('pt_subscription_first_payment', $screen->id, 'normal');
	//Hide the "Payment items" meta box.
	remove_meta_box('pt_payment_items', $screen->id, 'normal');
	//Hide the "Customer details" meta box.
	remove_meta_box('pt_customer_details', $screen->id, 'normal');
}

add_action('add_meta_boxes', 'plt_hide_paytium_metaboxes', 20);