See the [currency list](https://woocommerce.github.io/code-reference/files/woocommerce-includes-wc-core-functions.html#source-view.475) for reference on currency codes.
Add this code to your child theme's `functions.php` file or via a plugin that allows custom functions to be added, such as the [Code Snippets](https://wordpress.org/plugins/code-snippets/) plugin. Avoid adding custom code directly to your parent theme's functions.php file, as this will be wiped entirely when you update the theme.