https://mycast.orb.com/orb/html/login.html, really easy to find. I use the app and love it. The only thing is I wish it was a tad bit faster. I do have about 28k mp3's though so that might be a reason why it takes a while.
Quick note, you access all of your files via your browser, there is no app to be installed onto your ppc as far as I know. You run the server app on your pc and log in over the air.