From within the Settings app, tap General.
Tap Software Update.
Tap Automatic Updates.
In the iOS Updates section, tap or swipe Automatically Install to ON.
With this option enabled, your iPhone will automatically download updates and install them when your device is connected to Wi-Fi, charging, and locked. If you want your device to download updates but wait on your approval to install them, enable Automatically Download instead.
You've completed the steps!
