How to Enable The WooCommerce Notes Field

Enabling the notes field in WooCommerce can be done with a tiny snippet of code in your child theme's functions.php file. 

Here's the snippet:
https://gist.github.com/clifgriffin/1f8f441e47ccc72675ff9cc394322b2f

Once you have added this snippet, you will see the notes field appear on the Payment Method tab like so: