Thanks, the custom fields that can I add are only address fields on the checkout. According the documentation, topic "Description":
With the user custom fields (both essential and business edition only), you will be able to personalize the information you can gather from your customers when they register while on the checkout process. For example, if you want to know their birthday, you can add a custom field for that...
I need add a last-name field for the user on the checkout when the user is registering.
Is that possible with the starter edition?
Regards.