How to update my iPhone 6 Plus?

To update to the maximum of iOS 12.5.7, please 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. 

iPhone 6 Plus can be updated to up to: iOS 12.5.7

You can check which version you have here:

Settings > General > About

You can see how to update here:

Update your iPhone or iPad - Apple Support

Hursh92 Said:

"How to update my iPhone 6 Plus?: My iPhone 6plus needed update"

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Updating an iPhone:

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 available, they will install, sure enough.