how can i update my iPhone 4s to iOS 9 or iOS 8?

An iPhone 4s can be updated to iOS 9.3.5 only at this point. You cannot update to iOS 8, or any previous iOS 9 versions. Instructions for HOW can be found here: https://support.apple.com/en-us/HT204204

If you’ve done this and ran into a problem, you need to say that and give details as to what occurred, if you got errors/what are they exactly, etc.

Hi

Your iPhone cannot be updated iPhone 4s is a old iPhone now

Upgrade iPhone when you can.

Cheers

Brian 🇬-1F1E7;

If you are unable to update your phone to iOS 8 or nine, it is most likely an iPhone 4, not a 4S.

What does it say in Settings>General>About>Model?