Go to Settings > General > Software Update > Automatic Updates. Turn on iOS Updates below Automatically Install and Automatically Download. When an update is available, iPhone downloads and installs the update overnight while charging and connected to Wi-Fi. You’re notified before an update is installed. Tap Install Now or Download and Install. If your iPhone is set up to download updates automatically, you'll see the Install Now option—tap it to install iOS 15. If not, tap Download and Install to download the update. Once the download is complete, tap Install Now to start the installation. Here's how to download iOS 15, with all the steps you should take care of before you upgrade. Download iOS 15: What devices are eligible for the update? If your current iPhone runs iOS aOuk.