How to update iphone 6 to ios 14..?

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

iOS 12.5.7 is the end of the road for the iPhone 6. It is not possible to install a higher iOS version.

Hello Afhsen3!

No iPhone, no matter the model, can be updated to iOS 14.

Kurtosis12 gives you all the info you need concerning updating your iPhone 6.

Good Luck!