As of August 1, 2016, Autodesk is transitioning to a subscription-based licensing model similar to other large software developers like Adobe. The new licensing can be confusing to manage. To help, Autodesk has released an eBook to get you up and running. It contains helpful tips and detailed step-by-step instructions.
http://download.autodesk.com/us/subscription/ADK-15015_Subscription_eBook_final.pdf