şunu eklermisiniz

// Display Fields
add_action('woocommerce_product_options_general_product_data', 'woocommerce_product_custom_fields');
// Save Fields
add_action('woocommerce_process_product_meta', 'woocommerce_product_custom_fields_save');
function woocommerce_product_custom_fields()
{
global $woocommerce, $post;
echo '
';
// Custom Product Text Field
woocommerce_wp_text_input(
array(
'id' => '_custom_product_text_field',
'placeholder' => 'Custom Product Text Field',
'label' => __('Custom Product Text Field', 'woocommerce'),
'desc_tip' => 'true'
)
);

//Custom Product Number Field
woocommerce_wp_text_input(
array(
'id' => '_custom_product_number_field',
'placeholder' => 'Custom Product Number Field',
'label' => __('Custom Product Number Field', 'woocommerce'),
'type' => 'number',
'custom_attributes' => array(
'step' => 'any',
'min' => '0'
)
)
);
//Custom Product Textarea
woocommerce_wp_textarea_input(
array(
'id' => '_custom_product_textarea',

'placeholder' => 'Custom Product Textarea',
'label' => __('Custom Product Textarea', 'woocommerce')
)
);
echo '
';
}