Insert Meta Slider into Header

Hello. I am trying to insert the Meta Slider plug-in into my header. These are the instructions that the meta slider site gives me:

How do I include a slideshow in the header of my site?
You will need to paste the “Template Include” code into your theme (you can find this in the ‘Usage’ section underneath the slideshow settings)

Go to Appearance > Editor in WordPress
Edit a file called ‘header.php’ (or similar)
Find the correct place to add it (for example above or below the logo)
Paste in the code and save.
If you want to include the slideshow on your homepage only, use this code:

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

Now, I understand and am able to get to the ‘header.php’. However, once I am there, I do not know where to insert the meta slider code into the header code. I am not well-versed in code and I do not want to seriously alter my blog.

Please help!!