How to install 11 version my iPhone 6s

You can update the iPhone 6S to iOS 15, see this Apple article: iPhone models compatible with iOS 15

iPhone models compatible with iOS 15.2 – Apple Support (UK)

Check iPhone type -> Go to: Settings -> General -> About.

Go to: Settings -> General -> Software Update.

how to install 11 version my iPhone 6s

Which iOS is the iPhone running now?

You can't. You can install iOS 15.x. Nothing earlier.

My aipon model apon5s and I wanted IOS 11.0 udate

An iPhone 5s can update to iOS 12.5.5.