When you first install Cloudmark DesktopOne in Basic Mode, you get automatic filtering for one email account and manual filtering for as many accounts as you like. You can use DesktopOne this way for as long as you like, free of charge.
To get more features, you can upgrade to Cloudmark DesktopOne Pro by purchasing an annual subscription to Cloudmark. This FAQ article lists the additional features you get when you purchase a subscription.
You will receive an email confirmation of your purchase.