Display custom field value on woocommerce product page

I know similar questions have been asked dozens of times but I’m just not understanding how to display custom fields. I’m using woocommerce and want to display a custom field value on product pages.

I add the custom field “current_promotions” and a value to a product, and have tried adding this to the content-product.php template, but I’m getting nowhere:

<?php $postid = get_the_ID(); ?>

<?php get_post_meta($post_id, $key, $single); ?>

Solutions Collecting From Web of "Display custom field value on woocommerce product page"