How to Update
Even though watchOS 5.2.1 isn’t packed with shiny new features or major improvements, it’s highly recommended that you still download and install to keep your Apple Watch running smoothly.
Users can download the update by charging their Apple Watch to at least 50 percent battery life, placing it on their charger, and keeping their iPhone nearby for the duration of the update. The update can be found in the iOS Watch app, under General > Software Update.