How do I update my iPhone7
How long will it take to update my iPhone7
Question marked as
You can upgrade directly over Wi-Fi
see Update your iPhone, iPad, or iPod touch
*Note point 4 which is accompanied by a graphic showing how the iOS 15 upgrade is offered below any update to a previous iOS installation.
or by connecting your iPhone to a computer
It takes as long as it takes, and depends in part on your download speed to acquire the installer.