Apple released watchOS 4.2 Developer Beta 3 to developers Monday. No feature changes have been announced with this release, making it a bug fix and improvement cycle that also keeps up with iOS 11.2 DB3, macOS High Sierra 10.13.2 DB3, and tvOS 11.2 DB3.
If you’re testing watchOS developer betas, you can instal the update by launching the Watch app on your iPhone, then go to My Watch > General > Software Update after you install iOS 11.2 DB2.