How to update my iPhone 11 to iOS 16?

Assuming you have a compatible device, see: Update your iPhone, iPad, or iPod touch - Apple Support

And: If your iPhone, iPad, or iPod touch won't update - Apple Support

If the above Apple articles do not help, please post back with relevant information. 

Turn on automatic updates

Go to Settings > General > Software Update.

Tap Automatic Updates, then turn on Download iOS Updates.

Turn on Install iOS Updates. Your device will automatically update to the latest version of iOS or iPadOS. 

Ensure that you have a STRONG wi-fi signal, that Low Power Mode is switched off and that your iPhone is connected to a charger throughout the process. 

Update iOS on iPhone – Apple Support (UK)

Not sure what you are asking exactly. I know that you want to update your phone to iOS 16, but what have you tried up to this point? Are you having an issue?

If you are just unsure how to go about doing it, then go to Settings > General > Software Update. If there is an update available then it will let you download and install it from there. You can also turn on "Auto Updates" here which will automatically update your phone to the newest version it will support when the updates are released. If there is something else that you are trying to find out what to do, then more information is needed and the more that you can give the better your chances will be of finding the help you are looking for

About software updates for Apple devices - Apple Support