Please how can I upgrade my iPhone6s to ios14

An iPhone 6S can be updated to iOS 15.7.1. To accomplish that, 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. 

Use a computer or the Software Update function in Settings to install 15.7.1. It's no longer possible to update to exactly 14.

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