Download the Find My iPhone app
Alongside the Settings on your iPhone for Find My iPhone, you can also download an accompanying app for free (click here to see the app in the App Store). The app is useful as it automatically shows you the locations of any devices using your Apple ID, as long as they have Find My iPhone activated. Once the app is installed, launch it and you'll be prompted to sign in with your Apple ID, and then you'll be shown a map with your devices listed. This is particularly useful if you've lost your iPhone, as it means you can use your iPad with the Find My iPhone app installed to find it.
Using the Find My iPhone app
When you've selected a device, you have a few choices open to you. Tapping Actions will show you several options. The first is an icon of a car, which will take you to the Maps app and plot a route directly to your iPhone.
The next option is Play Sound, which will do exactly that. This is most useful if you've lost your iPhone somewhere around the house, or are having trouble tracking it down when you reach the location after following the route plotted on Maps. Tapping the icon will cause your iPhone to beep loudly, making it easier to find.
Lost Mode enables you to enter a passcode to remotely lock the device. This prevents anyone who finds your iPhone from gaining access to your data. You can unlock it using the same code when you finally recover the device.
The final choice is Erase Phone, which as the name suggests is something of a nuclear option. Tapping this will wipe all data from the device and should only really be used if you think it's been stolen, or has particularly sensitive information stored onboard. As this deletes all information, including your Apple ID, once you press that the device will disappear from your Find My iPhone list, and most likely your life.
How to use Find My iPhone on your computer
If you don't have another Apple device, that doesn't mean you can't track your iPhone down. The iCloud website (https://www.icloud.com/) gives you access to Find My iPhone, alongside other features such as iWork apps, Mail, Calendar and iCloud Drive. To use it, simply log in with your Apple ID, launch the Find My iPhone app and you'll see a map with the location of your device displayed. Click the green dot and you'll see the same three options presented to you on the app: Play Sound, Lost Mode and Erase iPhone or iPad.
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