I went around it, because I do not know how to use the custom fields either
Go to components/com_virtuemart/views/productdetails/tmpl/default.php and open it with Dreamweaver, preferrably, or some type of color-coded HTML/PHP editor so you can find it easier.
Find this code for the manufacturers link:
<?php
// Manufacturer of the Product
if (VmConfig::get('show_manufacturers', 1) && !empty($this->product->virtuemart_manufacturer_id)) {
echo $this->loadTemplate('manufacturer');
}
?>
I placed this code:
<!-- SKU Number -->
<div class="skuNumber"><br />
<?php echo JText::_('COM_VIRTUEMART_CART_SKU') ?>: <?php echo $this->product->product_sku; ?>
</div>
Be careful when messing around in these .php files, especially this one! This is your product details page. Hope this helps! I also hope there's an easier way.