After four months of testing and many betas, Apple has finally released watchOS 3 to the public. This version brings things like scribble for writing words in the messages app, dock for keeping apps running in the background, faster opening of apps, new watch faces, and more.
To download and install watchOS 3 your iPhone will first need to be on iOS 10. Then go to the Watch app > General > Software update > watchOS 3. The update isn’t too large, but it may take some time to download. Keep in mind that your watch will need to be at 50% and connected to a charger in order to install.