at the link you provided it says "both essential and business edition only"
www.hikashop.com/support/support/documen...shop-field-form.html
With the product custom fields (both essential and business edition only), you will be able to personalize the information for your products. Your potential customers will be able to see those on the product page. Also, with the filtering module, which will be available in a later release, your customers will be able to filter your products using filters based on those custom fields.
we are running essential, i want to add a simple text field to a specific product, i was told the essential version would do this, that is why i bought it. please see image above
help please