You can use the
dzwonek Maker application to make your own ringtones. It shows a list of all the sound files on your device, including the one you want to make. In addition, the app allows you to change the portion of the track that will be played as the incoming call. You should select a 30 second length for your resulting 'ringtone'. You can also zoom in on the wave graph to see how it sounds when played.
There are various ways to add your own ringtone to your phone. First, you need to find a ringtone that you like. There are websites that offer dozens of downloadable 'ringtones'. Some sites charge you for the right to use the music, while others let you download the song for free. Another option is to download older songs, as their copyrights have expired and have become part of the public domain. Then, you can load them onto your phone using a data cable or send them over the airwaves.