yoo! sorry for just replying to this now. the graveyard part is for sure a bit confusing!!! 🐸🐸
Once you have the 'Private Key', the 4th part of the puzzle is found in the crypt in the bottom right area of the graveyard (it's sort of fenced off)
u can skim through this playthru video here to check if u are still stuck:
hope that helps!!!!