Right after the installation, Plesk uses a trial license key. To get a new license key, proceed to the Plesk online store (shop.plesk.com) where you can select and purchase a necessary license key.
Once you purchase the key, you will receive an activation email with your activation code and a license key file. You can install a Plesk license key either by entering the activation code or by uploading the file from this email.
To install a license key using an activation code:
To install a license key using a license key file: