Twenty Fifteen

Recommended slideshow settings:

Steps

Go to Appearance > Editor. Select header.php from the right.

Find:

<div id="content" class="site-content">

1	<div id="content" class="site-content">

Insert below:

<?php 
    if (is_home() || is_front_page()) {
        echo do_shortcode("[metaslider id=123]"); // replace 123 with your slideshow ID
    }
?>

<?php

if (is_home() || is_front_page()) {

echo do_shortcode("[metaslider id=123]"); // replace 123 with your slideshow ID

}

Save.

Screen Shot 2015-01-21 at 11.32.19