First of all, you need to go in under Preferences and select "Allow multiple instances".
After that, create a bat file in your BSPlayer directory with the following contents:
Code:
bsplayer.exe <path to file 1>
bsplayer.exe <path to file 2>
bsplayer.exe <path to file 3>
bsplayer.exe <path to file 4>
After that, just run the file and place the windows in different places on the screen and click Repeat until you get it the way you want.
To my knowlege there is no way of syncing several instances of BSPlayer.