The service, which costs $15 USD per month, can be purchased through Apple or Cablevision's Optimum Online. To purchase HBO Now through Apple, you'll have to download the app on one of the devices listed above. Once you register your account and set up login credentials, you'll have access to HBO Now's catalog of movies and television series through your Apple devices, as well as HBONOW.com on your Mac or PC.
HBO Now includes access to over 2,000 movies and television series, including Game of Thrones, Silicon Valley, The Sopranos, The Wire, and more. Thankfully, the service has launched in time for Games of Thrones' Season 5 premiere, which airs April 12.
The app is currently only available on Apple devices, but that will change in the future, as Apple's exclusivity deal with HBO only lasts three months.