how to turn off my apple watch

See Turn on and wake Apple Watch - Apple Support

including the following from that link:

Turn off: Normally, you’ll leave your Apple Watch on all of the

time, but if you need to turn it off, press and hold the side button

until the sliders appear, then drag the Power Off slider to the right.

or if you mean the Always On option, see:

Always On lets Apple Watch display the watch face and time, even when

your wrist is down. When you raise your wrist, Apple Watch functions

fully.

1. Open the Settings app on your Apple Watch.
2. Tap Display & Brightness, then tap Always On.
3. Turn on Always On.
4. Turn on Hide Sensitive Complications to hide calendar events, messages, heart rate, and more when your wrist is down.