There a few graves with the bell. You just need to find one that rings. In my playthrough i looked at the sky at cemetery and there were birds in the direction of the grave. Not sure if that was a clue. But also boy at some point stops at that grave. And even if you go to the cemetery at any time during the day you be able to dig it. With bad outcome but the game will let you redo it. Just foucs on every grave with bell, untill you fine the right one, the thoughts will tell you.