The ability to use, activate and download Autodesk software is all controlled through the Autodesk Account. All users and managers must have an Autodesk Account; the user type generally determines what steps need to be taken to set up your software.
During product activation after the installation you will be asked to sign in using your Autodesk Account credentials. You will need an active internet connection to activate the software and begin using it.
If the purchaser is not the user then the purchaser will need to sign into their Autodesk Account and click on the users button.