Once you upgrade your iPhone to iOS 10 you can see the watchOS3 upgrade. It worked that way for me but not sure if I needed to upgrade my phone or not. You need your watch and iPhone to connect over Wifi and that the watch is connected to its charger and you are good to go.
Here is the new stuff:
For whatever reason, it took to two tries to do my upgrade. But it did work fine – but did take a bit of time!
- 9/13/16 – I have heard comments elsewhere that the watchOS update took five hours. Mine took about 1.5 hours. I have heard from others that 1 – 2 hours seems ‘normal’.
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