Go to editor option under appearance menu. There you can find the header.php for your theme.
many thanks for the hints – great!!!
where to put the code snippet
[metaslider id=36]
<?php
/**
* The Header for our theme
*
* Displays all of the <head> section and everything up till <div id="main">
*
* @package WordPress
* @subpackage Twenty_Fourteen
* @since Twenty Fourteen 1.0
*/
?><!DOCTYPE html>
<!--[if IE 7]>
<html class="ie ie7" <?php language_attributes(); ?>>
<![endif]-->
<!--[if IE 8]>
<html class="ie ie8" <?php language_attributes(); ?>>
<![endif]-->
<!--[if !(IE 7) | !(IE 8) ]><!-->
<html <?php language_attributes(); ?>>
<!--<![endif]-->
<head>
<meta charset="<?php bloginfo( 'charset' ); ?>">
<meta name="viewport" content="width=device-width">
<title><?php wp_title( '|', true, 'right' ); ?></title>
<link rel="profile" href="http://gmpg.org/xfn/11">
<link rel="pingback" href="<?php bloginfo( 'pingback_url' ); ?>">
<!--[if lt IE 9]>
<script src="<?php echo get_template_directory_uri(); ?>/js/html5.js"></script>
<![endif]-->
<?php wp_head(); ?>
</head>
<body <?php body_class(); ?>>
<div id="page" class="hfeed site">
<?php if ( get_header_image() ) : ?>
<div id="site-header">
<a href="<?php echo esc_url( home_url( '/' ) ); ?>" rel="home">
<img src="<?php header_image(); ?>" width="<?php echo get_custom_header()->width; ?>" height="<?php echo get_custom_header()->height; ?>" alt="">
</a>
</div>
<?php endif; ?>
<header id="masthead" class="site-header" role="banner">
<div class="header-main">
<h1 class="site-title"><a href="<?php echo esc_url( home_url( '/' ) ); ?>" rel="home"><?php bloginfo( 'name' ); ?></a></h1>
<div class="search-toggle">
<a href="#search-container" class="screen-reader-text"><?php _e( 'Search', 'twentyfourteen' ); ?></a>
</div>
[metaslider id=36]
<nav id="primary-navigation" class="site-navigation primary-navigation" role="navigation">
<button class="menu-toggle"><?php _e( 'Primary Menu', 'twentyfourteen' ); ?></button>
<a class="screen-reader-text skip-link" href="#content"><?php _e( 'Skip to content', 'twentyfourteen' ); ?></a>
<?php wp_nav_menu( array( 'theme_location' => 'primary', 'menu_class' => 'nav-menu' ) ); ?>
</nav>
</div>
<div id="search-container" class="search-box-wrapper hide">
<div class="search-box">
<?php get_search_form(); ?>
</div>
</div>
</header><!-- #masthead -->
<div id="main" class="site-main">
