On the Status page you can buy a license by clicking on the lower link in the license panel. 

Then you have to select the correct license type. Click on the orange button to buy the selected license. 

You will be forwarded to an encrypted web page of Digital River, who sells the license. After your purchase you will receive a license file by email. Save this license file on your Windows Home Server in the share \\Server\Software\Add-Ins.

Now load this license with a click on the "Load license" link: 

Enter your email address in the next dialog and load the license file: 

Operation of Lights-Out