How can i get ios 15 in my iphone

Please take a look at this article for info about iPhone models compatible with iOS 15.

iPhone models compatible with iOS 15.5 - Apple Support

Hey! I understand your frustration. If you click on Settings>General>Software Update. You should be able to update!

It's important your device can support iOS 15. Only the iPhone 6S and above support iOS 15.

An iPhone 6 Plus isn't capable of 13 or above.

(218755)

Sadly your iPhone 6 does not support iOS 15.