Photo Ephemeris Web is a web application, meaning it runs in your web browser.
There's nothing to download and nothing to install.
In order to subscribe, you're already signed into the web app and have it running successfully.
When your subscription is processed, we updated your account details on our server to enable all the PRO features. You can start using them immediately - you'll find that any feature that previously required was shown with a 'PRO' badge is now available for you to use.
If you have any trouble finding what you need, or have any questions, get in touch!