Required Background modes key is not there in info-plist file

I want to set required background mode key value so that my app also works in background. Actually i want to get the user location updates when the app is in background, but there is no key called required background mode key in my info-plist file. How to set this key and jow to bring this in my file?

In Xcode 5, Project setting -> Target -> Capabilities -> Background modes -> check Location updates.

If you are using an earlier version of Xcode, set the background mode for Location as in the following screenshot.