1. Save the desired ringtone in the .m4r format to your computer.
2. Connect your iPhone to your computer and open iTunes.
3. Go to the iTunes' Preferences menu and confirm that "Tones" is displayed in your iTunes library.
4. With the Tones library selected, drag and drop the .m4r file into iTunes.
5. Click on your iPhone in iTunes and click the Tones menu. Check "Sync Tones," and select either "All tones" or "Selected tones." If you choose to sync only "Selected tones," you will need to make sure that your desired tones are individually checked from the list.
6. Click "Apply" to sync the tone onto your iPhone.
7. Once synced, go into Settings in your iPhone. Click on Sounds and then on Ringtone. Your Call of Duty®: Ghosts ringtone should now be listed!