My brother's phone got stolen. I tried locating it with "Find My iPhone" but the app doesn't show up so I guess it's not installed on his device. I don't think we ever connected his device to iTunes. Is there a way to download the app to his device or use my iPhone to find his, or any other way to find it? The phone company says the thief is still using the internet on the device and today he accidentally called me when I was sleeping so I couldn't answer. When we call it, he doesn't pick up. So I just really need to find it! :/
Sorry, but if Find My iPhone wasn't enabled on his iPhone at the time it was stolen, there's not much you can do to track it, as you can't remotely enable Find My iPhone.
Even if you could push an app to the phone, it's not possible to enter the iCloud account. Your option is to pursue legal means to compel the phone company to either track the device or terminate the service.