How do I set up an additional user on my account (I have paid for more than 1 user)?

Hi,

You have indeed upgraded to a "Premium" account and can now share forms with sub users.  Here is our guide on how to do so:

http://www.jotform.com/help/232-How-to-Share-Forms-with-a-Sub-Account-User

If you have any issues using this feature, let us know and we will be happy to help.