It depends where your mp3's are. To my knowledge you can only open mp3's that are in your shared folders (unless you want to trial one that's dwnlding.) (Happy to be corrected here!) Your shared folders will be listed in your LW Library window. Just press the arrow to open the folder or just click onto it (depending how many levels down the mp3s are) & your mp3's should be listed in the pane to the right. Click onto an mp3 & press launch. Once launched it can be controlled by the media player control.

If you want to add xtra shared folders, go to your LW menu Tools-Options & Sharing. There you can press Add & direct lw to where this new folder is. Then press Open & Apply & ok. Go to your LW Window & press Refesh & your new share folder will have been added to the list.

Hope this helps.

Actually, I just realised you can put the files into your incomplete folder & they can be played from there. That's if you don't want to share them (or perhaps you're aleady sharing your incomplete folder.)