How to update my iPhone 6s to iOS 16?

Update your iPhone, iPad, or iPod touch

• If you have an iPhone 5S or 6/6plus, the highest you can update to is 12.5.7

• If you have an iPhone 6S through 7, or SE 1st generation, you can update to 15.8.2

• If you have an iPhone 8 or X, you can update to 16.7.7

• If you have an iPhone SE (2nd generation or later), or XR through 15, you can update to 17.4.1

Go to Settings > General > Software Update.

This link will show you how to update your iPhone, iPad, or iPod touch using WiFi -

Update your iPhone or iPad - Apple Support

This link will show you how to update using your computer -

Update iOS on iPhone - Apple Support

If you want to run iOS 16, you will need to have at least an iPhone 8 or higher model.

You don't. The iPhone will need to be upgraded. It has always been the case that software outpaces hardware and it always will. Your current iPhone simply does not have the power to run a newer iOS version.

I want to update

That iPhone is too old to run iOS 16 I am afraid

What can I do

Buy an iPhone 8 or higher model.

How to update my iPhone 6s to iOS 16

It's been answered. And the answer is you don't. Because you can't.

This is a one page thread. Read the posts with the answer already provided.