Hi there Jack1879,
We're happy to help with your iPhone. To start, you'll want to be sure you have a working, reliable Wi-Fi network connection, connect your iPhone to power, and allow the update to complete.
If the download takes a long time
You need an internet connection to update your device. The time it takes to download the update varies according to the size of the update and your internet speed. You can use your device normally while downloading the update, and your device will notify you when you can install it. To improve the speed of the download, avoid downloading other content and use a Wi-Fi network.
Have a look at this support article to learn more: If your iPhone or iPad won't update - Apple Support
If that doesn't seem to help, we'd like to learn more to continue working toward a solution. Are you seeing the Apple logo and a progress bar on your iPhone, as if the update is attempting to install? Is your iPhone restarting repeatedly? Which iOS version is installed currently? You'll find that listed in Settings > General > About, next to Software Version.
If your iPhone appears to be stuck on the Apple logo, you'll want to follow these steps to resolve the issue:
1. Make sure that the progress bar on your iPhone screen hasn't moved for at least one hour.
2. If the progress bar hasn't moved for more than one hour, connect your device to a computer, then put your device into recovery mode with these steps:
- iPhone 8 and later: Press and release the Volume Up button. Press and release the Volume Down button. Press and hold the Side button. Keep holding the Side button until you see the recovery mode screen.
3. On a Mac with macOS Catalina 10.15 or later, open the Finder. On a Mac with macOS Mojave 10.14 or earlier, or on a PC, open iTunes. When asked to update or restore, choose Update. This will update your device to the latest version of iOS. If you choose Restore, it will erase your iPhone.
You'll find these steps and more information here: If your iPhone is stuck on the Apple logo - Apple Support
Take care.