It’s worth noting that both iOS 16 and WatchOS 9 betas have been available for a while, but the operating systems are now available for the wider public to download.
The only prerequisite to downloading iOS 16 is having a compatible device. iOS 16 can be downloaded on the iPhone 8, iPhone 8 Plus, iPhone X, iPhone XS, iPhone XS Max, iPhone XR, iPhone 11, iPhone 11 Pro, iPhone 11 Pro Max, iPhone 12, iPhone 12 mini, iPhone 12 Pro, iPhone 12 Pro Max, iPhone 13, iPhone 13 mini, iPhone 13 Pro, iPhone 13 Pro Max and the iPhone SE (2nd and 3rd gen).
To download iOS 16, head to Settings > General > Software Update > Install.
Similarly, the only prerequisite to downloading WatchOS 9 is having a compatible Apple Watch. WatchOS 9 can be downloaded on Apple Watch Series 4 or later released devices.
To download WatchOS 9 on your Watch, open the Watch app on your iPhone > Tap on General in My Watch > Software Update > Install.
Learn more about WatchOS 9 here.
Learn more about iOS 16 here.