How can I do to install this iOS 15.8 on my iPhone

tetteh257 wrote:

How can I do to install this iOS version

To get the most recent available version for your iPhone:

Here is how to: Update your iPhone or iPad - Apple Support

And what to do: If your iPhone or iPad won't update - Apple Support

An iPhone 6s can be updated to the latest version of iOS 15 for instance, but not to iOS 16 or later.

if you have used the software update function and have the most recent available version, then you have the latest version for your iPhone.

Here is how to: Update your iPhone or iPad - Apple Support

And what to do: If your iPhone or iPad won't update - Apple Support