Q: I can't get my find my phone app on line

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iCloud: Troubleshooting the Find My iPhone app

iCloud: Troubleshooting Find My iPhone, iPad, iPod touch, or Mac

You'll have to have at least one device running iOS5, to be able to install the app on other devices, because you'll need to be able to use iCloud.

Locate your missing iPhone with Find My iPhone.

I don't quite understand what you want to do. The Find my iPhone app is so you can find one iPhone from another iPhone. You do not need the app to enable Find my iPhone for your phone; just go to Settings/General/iCloud and turn it on. You then can use iCloud in a browser on your computer to find your iPhone. If you have a SECOND iPhone you can put the app on it to find the first iPhone (and vice versa).

Did you try to log into iCloud on your computer while your phone is connected to Wi-Fi or the Cellular network?

Any restrictions for location services set up on your phone in Settings/General/Restrictions?

The "Find my iPhone" app will also locate and show the device on which it is installed, all devices registered to your iCloud account will be shown.