I just checked their website and there doesn't appear to be a downloadable manual. It looks like it is a fairly simple player. It is similar to a usb thumbdrive except you can listen to music on it. Actually, you could probably store data on it. You shouldn't need any additional software. You should be able to drag and drop your tunes onto the player via windows explorer. It plays mp3s and wmas (not the protected kind, it's not "Plays For Sure" certified).
Here's a link to Buslink's product page, just in case you haven't gone there yet:
i am looking for a guide for a buslink sk256m mp3 player,i bought a used one and it didn't come with a guide,it is a mp3 & fm player,can anyone please help me...WESTCOASTPOPS@CHARTER.NET