To update your watch, your battery needs to be charged to at least 80%. Once you receive the update notification, press "Download" and the update will begin.
The build number for Android Wear 5.0.2 on the Moto 360 is LWX49L For the Gear Live it is LWX49K. Owners of other Android Wear flavored timepieces like the LG G Watch and ASUS ZenWatch should keep their eyes open for the update, which could come at any time.
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source: ModYourPhone (translated)