woocommerce_wp_text_input.php

<?php
/**
 * Display a custom text field
 * @since 1.0.0
 */
function cfwc_create_custom_field() {
	woocommerce_wp_text_input(
		array(
			'id'            => 'custom_text_field_title',
			'label'         => __( 'Custom Text Field Title', 'cfwc' ),
			'class'		=> 'cfwc-custom-field',
			'desc_tip'      => true,
			'description'   => __( 'Enter the title of your custom text field.', 'ctwc' ),
		)
	);
}
add_action( 'woocommerce_product_options_general_product_data', 'cfwc_create_custom_field' );