D.H.
Thank you for posting in the Clarizen Forum. The User Type/Roles and Licenses are frequently asked about. I am sure you looked at this information but here is a link to where you can find information about this in the documentation...
http://usermanual.clarizen.com/#1-4-1-about-user-types/roles
This link will take you to chapter 1.4 of the User Manual. Also check out chapter 1.5, specifically the License types image that shows you some information about differences between the Licenses available.
As for the issue with changing the License, you cannot simply change it. There is a specific way to do this based on the current license the user has.
Go to the People Module and highlight the user in question. Then, if the User's current license is NONE or EMAIL, then you should be able to simply add the license by clicking on the Admin link above the toolbar and then going to the Licenses button (drop down). From there you will be able to Assign licenses to users and IF license of a different type are currently assigned, you can revoke the current license to release it and then you will be able to Assign a new license to the user.
Sincerely,
Boris Krutiy