If you have not gotten through the cemetery's puzzle with the plates then you haven't gotten far enough to need it yet. I don't have it yet but I'm through that part and haven't hit a dead end yet. If you are further, sorry was just trying to help out.
You need to navigate through the cemetary. Look for the area where you go through all the different tombs. Make sure you look carefully in each one to see if you can shimmy through the wall or into a hole on one of the sides. You'll get through.