Hey @alfred here is your answer
For creating a custom checkout template for WooCommerce there are two methods by using the plugin and by adding custom code in your theme file.
By Custom code :
First, you need to create a “WooCommerce/checkout” folder inside your theme folder. I suggest you to before changing in core theme file create a child theme and perform the steps in the child theme.
Then copy the WooCommerce checkout page template, from “woocommerce/templates/checkout/form-checkout.php” and write the code according to the requirements of your field.