How to update iOS on iPhone 6
I want to upgrade my iPhone ios
[Re-Titled by Moderator]
iPhone 6, iOS 12
To update to the most recent, compatible version 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.