Apple has posted watchOS 2.2 for the Apple Watch. It allows iPhones running iOS 9.3 to pair and swap between multiple Apple Watch models. It also sports an enhanced Maps app.
To upgrade, connect your Apple Watch to power, and keep it on the charger until the update is complete. On your iPhone, open the Watch app, tap the My Watch tab, then tap General > Software Update. If asked for your iPhone passcode or Apple Watch passcode, enter the passcode.