watchOS 4.2.3 can be downloaded through the dedicated Apple Watch app on the iPhone by going to General --> Software Update. To install the update, the Apple Watch must have 50 percent battery, it must be placed on the charger, and it must be in range of the iPhone.
Today's update addresses minor bugs discovered since the release of watchOS 4.2.2, and it includes a fix for a bug that causes device crashes when a specific character in the Indian language Telugu is sent, received or input into an app. Similar fixes have also been released for macOS High Sierra and iOS 11.
watchOS 4.2.3 will be succeeded by watchOS 4.3, an update that's currently in beta testing and slated for release in the spring. watchOS 4.3 introduces portrait orientation support for Night Stand mode, and it reintroduces support for controlling music played on the iPhone with the Apple Watch.