How Do I Install Apple Watch Updates?
In order to update your Apple Watch you will need your iPhone connected to a Wi-Fi network, the Apple Watch charger, and a minimum of 50% battery life on your Watch.
Once that's squared away, launch the Apple Watch app on your iPhone and navigate to My Watch > General > Software Update. If there is an update available, hit the Download and Install button to begin downloading the update. Once the update is ready to be installed, plug your Apple Watch into its charger and make sure it's in range of the iPhone, then begin the update. The Apple Watch screen will change to indicate the update is happening. Once it's finished the Watch should reset itself to show that it's finished.