When you purchase a Parallels Desktop Enterprise Edition license, you must register it with a Parallels Business Account to activate Parallels Desktop installations with it.
To create a Parallels Business Account, go to this page and select the I am a new user option. Once you log into your customer dashboard, select the Register Key option in the top-right corner. Enter your purchased key, add a display name, and click Register.
The information about your Parallels Desktop Enterprise Edition license and setup will appear in your dashboard, and you can proceed with the deployment process.