Custom Fields for WooCommerce Single Product Page https://wpsites.net/free-tutorials/single-product-page-custom-fields-for-woocommerce/

wc-single-product-custom-fields.php

add_action('woocommerce_product_options_general_product_data', 'add_custom_fields');
function add_custom_fields() {
    woocommerce_wp_text_input( array(
        'id'          => '_shipping_detail',
        'label'       => 'Shipping Detail',
        'desc_tip'    => 'true',
        'description' => 'Enter the shipping details.',
    ));

    woocommerce_wp_text_input( array(
        'id'          => '_manufacture_info',
        'label'       => 'Manufacture Info',
        'desc_tip'    => 'true',
        'description' => 'Enter the manufacture information.',
    ));

    woocommerce_wp_text_input( array(
        'id'          => '_product_terms',
        'label'       => 'Terms',
        'desc_tip'    => 'true',
        'description' => 'Enter the terms.',
    ));
}

add_action('woocommerce_admin_process_product_object', 'save_custom_fields');
function save_custom_fields($product) {
    if (isset($_POST['_shipping_detail'])) {
        $product->update_meta_data('_shipping_detail', sanitize_text_field($_POST['_shipping_detail']));
    }
    if (isset($_POST['_manufacture_info'])) {
        $product->update_meta_data('_manufacture_info', sanitize_text_field($_POST['_manufacture_info']));
    }
    if (isset($_POST['_product_terms'])) {
        $product->update_meta_data('_product_terms', sanitize_text_field($_POST['_product_terms']));
    }
}

add_action('woocommerce_single_product_summary', 'display_custom_fields', 25);
function display_custom_fields() {
    global $product;
    $shipping_detail = $product->get_meta('_shipping_detail');
    $manufacture_info = $product->get_meta('_manufacture_info');
    $product_terms = $product->get_meta('_product_terms');

    if ($shipping_detail) {
        echo '<p><strong>Shipping Detail:</strong> ' . esc_html($shipping_detail) . '</p>';
    }
    if ($manufacture_info) {
        echo '<p><strong>Manufacture Info:</strong> ' . esc_html($manufacture_info) . '</p>';
    }
    if ($product_terms) {
        echo '<p><strong>Terms:</strong> ' . esc_html($product_terms) . '</p>';
    }
}