Instructions
Scroll to the Open Manager option in the XMB menu on your PS3 display.
Select the "Split BIG files to .666xx" to select the desired game folder. Navigate through the subfolders within the main game folder, using the "Up/Down" arrow buttons on your game controller, to locate the file you want the split. Press the "X" button on your controller to select a file.
Select the checkbox labeled "Don't delete splitted BIG / merged .666xx files," then press the "X" button on your controller to begin the file-split.