Licenses are Pay-what-you-want, you can even take one for free if you like.
To get one, go to:
Then click Get a License.
The storefront will pop up, enter how much you want to pay (0 if you like), then continue through the process.
Once complete you will be given a license code (it will also be sent via email).
Tip: if you want to pay, but would rather use PayPal, you can enter 0 on the storefront page and donate here:
PAYPAL DONATION WILL NOT GENERATE A LICENSE KEY. You still need to go to the main storefront and enter 0 then only your email will be required.
Once you have the license code, open up the Portals main window (if portals is running but its not open, click the taskbar icon to open it).
Go to the License page and click Configure License:
Enter your code then click Activate License:
You will then be good to go!