iCloud: Set up Find My iPhone
Before you can use Find My iPhone to locate your devices, you need to turn it on on each of your iOS devices and Mac computers. Find My iPhone requires iOS 5 or later (iOS 6 is required for Lost Mode), or OS X v10.7.5 or later.
Set up Find My iPhone on 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 that appear.
Tap to turn on Find My iPhone (or Find My iPad or Find My iPod), and when asked to confirm you want this option, tap Allow.Tip: For added security, set up a passcode that needs to be entered before anyone can access the apps and information on your device (Settings > General > Passcode Lock). You can also turn on Restrictions to prevent anyone else from turning off Find My iPhone (Settings > General > Restrictions).
Set up Find My iPhone on 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 an Apple ID,” then follow the instructions that appear.
Select the Find My Mac checkbox, then confirm that you want to allow Find My iPhone to use the location of this Mac.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.
Now you can use Find My iPhone to locate the devices you set up.