There are 2 ways available for you to upgrade your iPhone or iPad to iOS 12
. Here's how:
1. Update the Software on iDevice
1st Step: Unlock your iDevice and go to "Settings > General > Software Update".
2nd Step: If there is an iOS version available, iOS will offer you the details. Just read it.
3rd Step: Click on "Download and Install" and then enter the passcode if required. After that, you should agree to the terms & conditions.
4th Step: Now the device will begin to download the update and you will receive a notification when the download is finished.
5th Step: Tap on "Details" followed by "Install Now". Then the iDevice will start to install the iOS 12. The update will take a while so please wait patiently.
2. Update to iOS by Using iTunes
1st Step: Make sure you have a recent iTunes backup and have encrypted it. Otherwise, your passcode or other data might be damaged or lost during the upgrade.
2nd Step: Open iTunes on your computer and then plug your iPhone/iPad to the computer with a USB cable.
3rd Step: On the main interface of iTunes, you can tap on the "your device" icon at the top left corner.
4th Step: Go to "Summary" section and tap on "Check for Update".
5th Step: Supposed there is an update available, please click on "Download and Update".
6th Step: After that, you should agree to the terms and conditions and type in the password on your iDevice if prompted.