The installation wizard allows you to enter your activation key during Parallels Workstation installation. If you have not done this, perform the following steps:

Parallels Workstation has been activated successfully. Thank you!" From this point on your copy of the Parallels Workstation is active and you may use all of its features and capabilities.The License information box describes your current activation status: inactive, active trial, expired trial, active permanent, expired permanent. If you have an active copy, trial or permanent, all license-related information is displayed here. The same information is contained in the License information group in About Parallels Workstation window and is described in the appropriate topic.
Getting an Activation Key
If you do not have a key, you can obtain one by clicking the Evaluate or Buy button that are provided in the Activate Product window.
To get an evaluation key:

Alternatively, you may register on Parallels site. Use the Register on site button to proceed to creation of the account on site. You will receive a free trial activation key on your e-mail soon after this.
To get a permanent activation key:
Click the Buy button to open the Parallels Online Store where you can purchase a permanent activation key.