Apple Watch Series 2
watchOS 4
1. Find "Siri"
Press the Digital Crown.
Press the settings icon.
Press General.
Press Siri.
2. Turn automatic activation on or off
Press the indicator next to "Hey Siri" to turn the function on or off.
If you turn on the function, you can activate Siri by saying "Hey Siri" when the screen on your Apple Watch is turned on. You can select more voice settings for Siri on your phone.
3. Return to the home screen
Press the Digital Crown twice to return to the home screen.