How will I update my iPhone

Hello ~ Take a look at link below as unfortunately your current iPhone 6 cannot be updated to iOS 14. Do some shopping for new IPhone if you require iOS 14 by going to top of screen here (black line above) and click on iPhone.

iPhone models compatible with iOS 14.7 - Apple Support

~Katana- San~

An iPhone 6 or 6 Plus model cannot be upgraded past iOS 12.5.4. If you need to run apps that require a newer version of iOS, you will need to upgrade your phone to a newer model.

You won't. Your nearly 8 year old iPhone 6 is too old, too underpowered and lacks the hardware to support iOS versions higher than 12.5.4.

Time for a newer, more modern iPhone at this point.