Losing any phone is a pain, but losing your iPhone means a significant cash outlay for a new one, plus the loss—and possible exposure of—personal data, your iTunes account, your photos, and all the hours you’ve already spent setting it up just the way you like. Perhaps, all is not lost! If your iPhone hasn’t been stolen—you have merely misplaced it—your chances of recovery are excellent, and we’ll show you how to do it.
Click on the Devices button. This is in the upper left of the screen, and will give you the option of choosing any enabled device. Your iPhone will be displayed in this list. Click on it, and Find My iPhone will search for your phone's location. Note: If the phone has been powered off, or the battery has run out, it will show you the last known location, but will not be able to show you the current address.
Erase all your data. Should you not be able to locate your phone, and suspect that it's lost, click on the Erase iPhone button in the phone's info window. This will erase all data, but you will not be able to use Find My iPhone to locate your phone once that happens. It's better that, however, than to have your personal information compromised. Should you later recover your phone, you can restore your data through your iTunes backup.