Initiate the upgrade
Just as you can back up your device via iTunes or directly from your device to iCloud, so too can you update your iPhone, iPad, or iPod touch through an iTunes connection or via iCloud. The latter is easier as you can do it over any Wi-Fi network and needn't be within cable-reach of your computer. Still, we'll show you how to do it both ways.
Install over the air
When a new iOS update becomes available, it isn't long before your iPhone, iPad, or iPod touch learns about it. Similar to the way the App Store seeks out new versions of apps you own, your device checks in with iCloud to see if a new iOS update exists. When it learns of such an update, a small red badge appears atop the Settings icon on the home screen.
To install the update, go to Settings > General > Software Update. On the resulting screen you'll be told that iOS 8 is available. Tap the Install button to start downloading and installing the update. (If you don't see the red badge on the Settings app but know that iOS 8 has been released, navigate to Software Update anyway. When you get there, your iPhone, iPad, or iPod touch will query the update server to see if a new version is available. If so, it will offer you the opportunity to install it.)
It's a good idea to update your device only when it has at least a 50 percent charge or, better yet, is plugged into a power outlet. You don't want your device to run out of power when it's half-way through installing a new version of its operating system.
Install from your computer
If you happen to be within reach of your computer you're welcome to install iOS 8 via iTunes. To begin, launch iTunes. If you're not using the Wi-Fi Sync option, string the syncing cable between your computer and your iOS device. iTunes should tell you that a new version of iOS is available for your device and offer to install it for you. If you see such a notice, choose to install the update.
If iTunes doesn't mention the update, click on the Summary tab and then click the Check for Update button. This will cause iTunes to query Apple's servers about the existence of any new updates. When it's alerted to one, you'll be told that the update is available. To install it, click the Update button. iTunes will then start downloading the appropriate version of iOS for your device. (Apple creates different versions of iOS 8 for each device and model. So even though you've download one copy for your iPhone 5s, you'll need to download a different version for your iPad mini.)
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