What's Find My iPhone?
Download Find My iPhone at App Store for free. You can download it exactly the same way you downloaded Voice4u.
Tap the Setting app on the Home screen.
Tap "iCloud". *If you are asked to sign-in, type-in your Apple ID (email and password). If you don't have an Apple ID yet, follow the guide on the screen.
Tap Find My iPhone (or "Find My iPod", "Find My iPad").
Also Try "Find My Friends" In case you want to have more privacy, or intend to share locations each other with multiple people, Find My Friends may be suitable. Find My Friends is also available at App Store for free.
How Do I Use?
Launch Find My iPhone and sign in with your Apple ID (Apple ID that is used on the device you want to locate).
Your mobile devices and computers are listed like this. Select one that you want to locate.
Your device is located on a map. You can zoom in/out the map. You can update its location by tapping the rounded arrow. Note that Find My iPhone tells us horizontal coordinate of devices, but not possible to find altitudes.
If You Lost It…
If you lost a device, or want to locate where it is now, launch Find My iPhone on another device. The screen on the right is Find My iPhone using on iPad.
You can also check in from a computer at iCloud.com.
In case you lose a device at somewhere away from where you are now, you can remotely lock it. Tap Lost Mode.
(optional) Type in a phone number where you can be reached. It will appear on the screen.
(optional) Type a message which will appear with the phone number typed in the previous step. Then, tap done.
Here is the screen of Lost Mode. When you find your device, you can unlock the device by typing your 4-digit passcode.