First, go into your 'Orders' screen and click on the order you made for your license. Highlight and COPY the serial number on that screen.
Next, go to:
http://viart.com/activation.php
Paste your serial number into the field and click go.
Below, it will create a link for you to download your serial number. Once downloaded, unzip the folder, and drag the license.php file into your includes folder on your server
Hope this helps.