Apple has released watchOS 5.3 to the public today, along with iOS 12.4. These changes are mostly bug fixes as Apple is actively working on watchOS 6 with betas already released to registered Developers. One important fix in watchOS 5.3 is the restoration of the Walkie Talkie app after a recent security risk was discovered.
To install the update, the Apple Watch needs to have at least 50 percent battery, it must be placed on the charger, and it has to be in range of the iPhone
iOS 12.4 brings preparation for the upcoming Apple Card in the summer and bug fixes ahead of iOS 13 in the fall.