The Nubia N3 sports a TF card memory card reader. If your laptop or personal computer can also read that card format (Most notebooks are so-equipped), you should be able to transfer music files
The ZTE Nubia N3 is an Android smartphone and the Android market offers a bunch of free ringtone apps such as MP3 Ringtone Maker, Zedge and more.
Here are links to some of the free ringtones (compatible with your ZTE Nubia N3) we offer:
Free Horror Ringtones Free Tropical Ringtones Free Ringtones-a-gogo Free Techno Ringtones Hear All Our Free Polyphonic Ringtones