How to register Apple Watch series 7
How do I register my watch
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What do you mean by registering your watch?
All that you do with a new watch is set it up properly with your iPhone.
Set up your Apple Watch - Apple Support
M1 Mac mini, macOS 12.4; Watch, series 5 GPS/cellular, watchOS 8.6; iPad Pro 2nd Gen, iPadOS 15.5; iPhone 12 Pro, iOS 15.5; TV 4th Gen, tvOS 15.5; HomePods, audioOS 15.5 and Airport Express w/ Airplay 2