How to update my ios from 10 to 11 on iphone 6

Click on this link to read how to "Update your iPhone, iPad, or iPod touch" --> https://support.apple.com/HT204204 - When you try to update you will only be given one update selection which will be the highest available iOS version supported by your device. If it says no update is available and you need a higher version you will have to buy newer equipment.

Since your phone can support iOS12 that will be the only option presented to you.

An iPhone 6 can only be updated directly to 12.5.1; this is done from a computer or the Software Update function in Settings.

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