iCloud: Set up Find My iPhone
Before you can locate your devices, you need to set up iCloud and turn on Find My iPhone on each of your iOS devices and Mac computers. Find My iPhone requires iOS 5 or later, or OS X v10.7.5 or later. For more information, see the Apple Support article System requirements for iCloud.
Set up an iOS device
On your device’s Home screen, tap Settings, then tap iCloud.
If you’re asked to sign in, enter your Apple ID or, if you don’t have one, tap Get a Free Apple ID, then follow the instructions.
If Find My iPhone (or Find My iPad or Find My iPod) is turned off, tap to turn it on.Tip: For added security, set up a passcode that needs to be entered before anyone can access the apps and information on your device. To set up a passcode, go to Settings > Passcode or Touch ID & Passcode. If your device has iOS 5 or iOS 6, go to Settings > General > Passcode Lock.
Set up a Mac
On your Mac, choose Apple menu > System Preferences, then click iCloud.
If you’re asked to sign in, enter your Apple ID or, if you don’t have one, click Create new Apple ID, then follow the instructions.
If Find My Mac is turned off, select it to turn it on.Tip: For added security, make sure your user account requires a password and that automatic login is turned off in Users & Groups preferences. For more information, choose Help > System Preferences Help.
When you set up Find My iPhone, Activation Lock is turned on automatically. Activation Lock makes it harder for anyone to use or sell your iPhone, iPad, or iPod touch if it’s ever lost or stolen. For more information, see the Apple Support article Find My iPhone Activation Lock in iOS 7.
If you’re having trouble with Find My iPhone, see the Apple Support article Troubleshooting Find My iPhone.