Here's how you can do this easily:
Log in to MyCommerce with the credentials that you used to purchase the Audials Gold Subscription. You forgot the password? Click "Request Login/Password".
You see your current Gold subscription under "My Account / Home". Click the reference number.
You see "Current conditions" and under "Available plans", you see the upgrade to the Audials One Ultra Subscription. Click "Checkout".
Restart your Audials One and enjoy the new AI features.