Download watchOS 8.4.2 Now With Bug Fixes and Security Updates
The update can be downloaded now through the companion Watch app on your iPhone by heading to General > Software Update in the My Watch portion of the app. You can also go to Settings > General > Software Update on an Apple Watch
Your watch needs to have more than 50 percent power and connected to a charger. Like most Apple Watch updates, it could take anywhere from 30 minutes to an hour to complete, so be patient.
It’s compatible with the Apple Watch Series 3 and later.
In release notes, Apple said the update offer unspecified bug fixes and security updates.