To recreate this we have to first begin with a new (graphic) symbol (Ctrl+F8). When the new symbol's stage has appeared, choose File> Import to import your image. Next we have to break the image apart. To do this simply select the image and press Ctrl+B.
Once this is done, open the library window (Ctrl+L).
Now right click on the bitmap symbol (not the graphic symbol) and select "properties" from the context menu.