Tips on Customizing Custom Field Template

How to Hide the "Custom Field Template" Admin Menu

function plt_hide_custom_field_template_menus() {
	//Hide the "Settings → Custom Field Template" menu.
	remove_submenu_page('options-general.php', 'custom-field-template.php');

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

Where do I put this code?

How to Hide the "Custom Field Template" Meta Box

function plt_hide_custom_field_template_metaboxes() {
	$screen = get_current_screen();
	if ( !$screen ) {

	//Hide the "Custom Field Template" meta box.
	remove_meta_box('cftdiv', $screen->id, 'normal');

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