When you say...
Sprint users can access the new enhanced Wi-Fi calling feature by downloading iOS 9.1, watchOS 2, or OS X 10.11.1 on their devices and making sure Wi-Fi calling is enabled on an iPhone by going to Settings --> Phone --> Wi-Fi Calling. Other devices can be set up to receive calls by going to Settings --> FaceTime --> Calls from iPhone. All devices must use the same Apple ID and they must be signed into iCloud.
It should be...
Sprint users can access the new enhanced Wi-Fi calling feature by downloading iOS 9.1, watchOS 2.0.1, or OS X 10.11.1 on their devices and making sure Wi-Fi calling is enabled on an iPhone by going to Settings --> Phone --> Wi-Fi Calling. Other devices can be set up to receive calls by going to Settings --> Phone --> Calls on other devices. All devices must use the same Apple ID and they must be signed into iCloud.