For Watch owners, the update can be downloaded by opening the Apple Watch iPhone app, navigating to the General menu and then selecting Software Update. The new version should install wirelessly.
Apple cautions that an iPhone should be connected to Wi-Fi, and that a Watch should be both connected to its charger and have at least 50 percent battery power.
The highlight feature of the new Apple Watch operating system is the ability for third-party apps to run natively on the wrist-worn device. This should allow software to run more quickly and operate more independently of the iPhone.
watchOS 2 also enables developers to create their own watch face complications. These will offer users the ability to add glanceable information, such as upcoming flights or sports scores.
Complications will also feature a new capability called "Time Travel," where users can rotate the Digital Crown on their Apple Watch to see information for later in the day, including calendar entries, weather, and more.
Apple also has a new feature called nightstand mode, which allows the Watch face to be viewed on its side for charging. When resting like this, the Digital Crown and side button can be used to snooze and end an alarm in the morning.
The update was originally supposed to be available on Sept. 16 alongside iOS 9. That same day, though, Apple issued a statement saying that it had discovered a bug that was taking "a bit longer to fix than we expected." At the time, it did not offer a deadline for the finished code.