I need to update my iPhone 6's iOS

An iPhone 6/6 plus can't be updated beyond 12.5.7, it doesn't have the hardware needed to run anything higher.

If you need a higher iOS version, you will have to purchase a newer phone.

To update to 12.5.7 -

Go to Settings > General > Software Update.

This link will show you how to update your iPhone, iPad, or iPod touch using WiFi -

Update your iPhone or iPad - Apple Support

This link will show you how to update using your computer -

Update iOS on iPhone - Apple Support

abrarfahim Said:

"i phone 6 ios update "

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IMPORTANT NOTE:

Keep Personal Info off of these Forums:

These forums are here for everyone out there to view. So, just be certain to keep personal information(Serial Number) off of these forums and other forums too. Anyone out there can read this info. For your Security & Privacy: I have asked the host to rid of the image you've provided.

So, Update Using a Computer:

Have a Computer Handy? If so, try using a computer to update. Go here: Update your iPhone Using a Computer - User Tip. If any updates are availabe, they will install, sure enough.