After being delayed nearly a week to fix a bug that was discovered at the last minute, Apple today released watchOS 2. It is a free upgrade for all Apple Watch users and it’s a pretty serious upgrade, making the previous watchOS 1 feel like a beta release. Most significantly, apps can run reduced dependence on your iPhone which provides a significantly faster and more seamless experience. Other significant additions are third party complications, FaceTime Audio calls, and photo watch faces.
To upgrade, you’ll need to upgrade your iPhone to iOS 9 first, then connect your Watch charge cable and make sure you have at least a 50% charge. Then on your iPhone go to Apple Watch > General > Software Update. Be forewarned that it’s a very slow upgrade process, sometimes taking half an hour to an hour.