do_shortcode Is a function which executes shortcodes in WordPress
In your case you should use it in your header.php file as the following:
<?php echo do_shortcode('[huge_it_gallery id="4"]'); ?>
do_shortcode Is a function which executes shortcodes in WordPress
In your case you should use it in your header.php file as the following:
<?php echo do_shortcode('[huge_it_gallery id="4"]'); ?>