Your question is both too vague and too general. Are you trying to create a visualization method, that is a manner for graphics to respond to the sound? That's not something you'd use DesktopX to create.
Are you trying to have an object display visualizations? That you can do with DesktopX, but you'll need to learn to script--DXPlayer doesn't currently support this. You'll need to choose which media player (iTunes, WinAmp, Windows Media Player, etc) you wish to use, and research how to interact with them via scripting at their respective sites.
Displaying playlists, as far as I know, is also not a feature of the DXPlayer plug-in. Their creation and display, though, is a more general problem than visualizations (not player specific), but getting the information from the list to the player is done in manners specific to the player you have chosen.
The only helpful advice I can give you is to look at the currently available DesktopX widgets. Find one that does things similar to what you want to do, import it into DesktopX Builder, and see how it does it.
