The Activatar web site is provided as an example, and not as a production site. You need to setup your own site with your own Web Server.
This is a Client-Server solution. The client side uses Activatar.dll to activate the software agains the server. During software activation, the client needs to connect to the server to validate the product key. That server needs to be managed
As you can see in the source code, there is a Client and a Server folder. The server folder contains a simple Web Service as an example, which is the same as the one installed in Activatar web site. Use that sample to create your
own Web Server replacing the RSA keys with the one you generate.
Note: The app.config in the sample application points to the Activatar online Web Server as an example. In a real application you will need to change the url to point to your own server.
I hope this clarify your question.