Tips on Customizing Simple Custom CSS and JS

How to Hide Simple Custom CSS and JS Admin Menus

function plt_hide_custom_css_js_menus() {
	//Hide "Custom CSS  JS".
	remove_menu_page('edit.php?post_type=custom-css-js');
	//Hide "Custom CSS  JS → All Custom Code".
	remove_submenu_page('edit.php?post_type=custom-css-js', 'edit.php?post_type=custom-css-js');
	//Hide "Custom CSS  JS → Add Custom CSS".
	remove_submenu_page('edit.php?post_type=custom-css-js', 'post-new.php?post_type=custom-css-js&language=css');
	//Hide "Custom CSS  JS → Add Custom JS".
	remove_submenu_page('edit.php?post_type=custom-css-js', 'post-new.php?post_type=custom-css-js&language=js');
	//Hide "Custom CSS  JS → Add Custom HTML".
	remove_submenu_page('edit.php?post_type=custom-css-js', 'post-new.php?post_type=custom-css-js&language=html');
	//Hide "Custom CSS  JS → Settings".
	remove_submenu_page('edit.php?post_type=custom-css-js', 'custom-css-js-config');
}

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

Where do I put this code?

How to Hide Simple Custom CSS and JS Meta Boxes

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

	//Hide the "Options" meta box.
	remove_meta_box('custom-code-options', $screen->id, 'side');
	//Hide the "Preview" meta box.
	remove_meta_box('previewdiv', $screen->id, 'normal');
	//Hide the "Apply only on these URLs" meta box.
	remove_meta_box('url-rules', $screen->id, 'normal');
	//Hide the "Code Revisions" meta box.
	remove_meta_box('revisionsdiv', $screen->id, 'normal');
}

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