Hi
There is no separate Siri app on the Home screen or Siri setting with the Watch app.
Follow the instructions here to use Siri:
Use Siri on your Apple Watch - Apple Support
If the feature does not operate as expected, then the following steps may help (check after each):
If you have not yet done so, update both your iPhone and your Apple Watch to the latest software, starting with your iPhone (be sure to make a backup first):
On your iPhone:
- Go to: Settings > Siri & Search - check the all desired settings are enabled.
- Go to: Settings > General > Restrictions - check that the restriction for Siri & Dictation is not enabled.
- Go to: Settings > General > Keyboard - check that Enable Dictation is turned on.
On your Apple Watch:
- When viewing the time on your watch, go to the Home screen by pressing the Digital Crown (round button) once.
- Go to: Settings (cog icon) > General > Siri > check that Hey Siri is turned on.
If you are using the "Hey Siri" command, check that you are using the feature correctly:
- To use Hey Siri on Apple Watch, the display must be awake.
- Wake the screen of your watch (by tapping it or by raising your wrist) and then say "Hey Siri".
Siri can also be activated via the Siri button on the Siri watch face or by pressing and holding the Digital Crown:
In order to use Siri on Apple Watch, check that your Apple Watch is connected as required:
Remove any protective case or film that you may be using on your Apple Watch if it is blocking the microphone port (the lower of the two ports on the opposite side to the buttons):
Clean your Apple Watch, paying particular attention to the microphone port, in case it has become blocked by debris.
Hold your Apple Watch closer to your face.
Restart your Apple Watch and iPhone, turning both devices off together, then restarting your iPhone first:
Follow the other steps here, under "If Siri doesn't respond or asks you to try again":
If the issue persists, having checked the settings above, next try unpairing and re-pairing your Apple Watch again:
If the issue still persists, then I suggest that you contact Apple Support (remote diagnostics and/or mail-in service may be available, if required), make a Genius Bar reservation or visit an Apple Authorised Service Provider for assistance: