How do I update my iPhone 7 to iOS 14?

To update to the most recent, compatible version of iOS, 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. 

NOTE: No Apple device can be updated to iOS 14.

Go to settings - general - software update and start there.

iOS 14 is not available for any phone at this time. What phone do you have and what is the current iOS version?

I phone 7