This article explains how to download and install new iOS updates using iTunes on a Mac or PC. It applies to iTunes 11 and later, and Macs running macOS Mojave (10.14) and earlier, and PCs running Windows 10 and later.
How to Update Your iPhone | Apple Support
If your Mac or PC has iTunes, you can upgrade to the latest version of iOS through the program. Using iTunes to update your iPhone or iPad is a good option if your iOS device is low on space.
Here's how to perform an iOS update using iTunes on macOS and Windows computers.
Connect the iOS device to the computer you're syncing it with and open iTunes.
