How to Upgrade the trial License Key
To upgrade the trial license key through the Panel interface:
Log in to Panel as administrator.
On Home page, click Tools & Utilities > License Management > Order New Key.
The online store will open in a separate browser window. In this window, select the items and features you want to include into your license and click Submit. In the next steps, indicate the currency, number of license keys, provide contact details, billing address, and payment method, and submit the form. The new key will be sent to the specified e-mail address.
Save the new key to the hard drive on your local machine.
Open again the License Management screen in Parallels Plesk Panel (Home > Tools & Utilities > License Management) and click Upload Key.
Reference: http://parallels.com/
How to install a license key through the command line interface.
To install a Panel license key using the Panel CLI, you should first upload it to the machine with the Panel, and then install it with the license utility.
license [--install|-i] [path-to-key-file]
For example:
1. On Linux/Unix:
./license -i /tmp/pp10key.xml
Reference: http://parallels.com/
How to install License Keys
To install a license key through the Panel graphical user interface:
On your Home page, click Tools & Utilities > License Management.
Click the Upload Key icon.
Specify the path to the license key file location: enter the path into the input box provided, or click Browse to browse for the desired location.
Select the Replace the currently installed license key with the selected one check box.
Click OK to submit.
The license key file will be upload to the Panel.
If you wish to upload keys for additional product features, select the Additional License Keys tab and upload the keys.
Reference: http://parallels.com/