If you are wondering how to add custom field in WooCommerce checkout page, you are at the right place.
Checkout Field Editor for WooCommerce plugin Nulled provides an easy way to customise (add, edit, delete and change display order) your fields displayed on WooCommerce checkout page. This plugin requires WooCommerce to be installed, activated, and configured.
Core fields can also be moved around giving you more control over your checkout without touching the code.
Demo : https://woocommerce.com/products/woocommerce-checkout-field-editor/