Check whether your iPhone model supports the latest iOS version
Back up your iPhone to iCloud or a computer
Connect your iPhone to Wi-Fi
Plug your iPhone into power
Open Settings
Tap General
Tap Software Update
Download and install the update if it is available
If the update is not available, wait for Apple to release it for your device and region
If you want beta software, enroll in the Apple Beta Software Program
Install the beta profile or use the beta update option in Settings if available
Restart your iPhone after installation if prompted