How to lock my Apple Watch SE?

To lock your Apple Watch SE, simply press the Crown button (on the right side of your device), and on the screen will appear watch face. Your Watch is locked right now. Alternatively, you can lock your Watch by a gesture. Simply cover your watch with your palm and the screen will turn off.

Other answers for questions you could be struggling with:

How to wake up my Apple Watch SE?
How to unlock my Apple Watch SE?
How to turn off my Apple Watch SE?