Do you mean the Binary object that comes with the engine? Found under "Data and Files"? Because a quick search around the forums suggests it's broken - you can write to it once, but that's it. Further writing just adds to the existing text, instead of replacing it, and deleting/clearing existing text doesn't work.
So if the player gets a high score of 1234, I can write that, and then read it just fine. But if they then beat it with a high score of 5678 and I try writing that, the high score will now read as 12345678 instead of 5678.