Using ringtones created from commercial songs may violate copyrights, especially if you don't own the rights for commercial use. Opt for legal sources to avoid legal problems. Go to your phone's ringtone settings, then select the option to set a ringtone. Browse through your available ringtones and choose the one you created or downloaded. Yes, most phones allow you to assign specific ringtones to different contacts. Consult your phone's manual to learn how to make this customization.