If you’re using a downloaded theme any changes you make may get overwritten by updates so you should create a child theme. There are plenty of tutorials available on how to do that. If your theme has been developed specifically for your site this won’t matter.
Open up the header.php file within your theme (wp-content/themes/THEMENAME/header.php
Work out where you want the total sales to appear and paste <?php echo do_shortcode(“[shortcode]”); ?>
Check your site to see if this is working correctly.
If you then need to format you’ll need to see what the shortcode is outputting and create CSS to suit. the default location for CSS is in styles.css