You should be in the Camp of the Free Crows, after defeating the Last Lord of Doors. After chatting with the crows here (and grabbing the Life Seed just north of the central campfire), head out of the camp via the southwestern doorway, and then go south a bit to the door back to the Hall of Doors.
Head east down the stairs, then up the northeast staircase to reach the main lobby where you defeated the Lord of Doors. There’s a key-lookin’ collectible on the ground in the middle of the lobby — grab it, then head up the stairs to the west to reach the door to the Lost Cemetery, and go through.
We’re going to head to the bell tower near where you enter the mausoleum (the path to the Urn Witch’s land). Head northeast from the door and up the stairs, then continue northeast through the open gate and up the ladder. Go north and climb the next ladder, then head up the nearby stairs into the graveyard. Head northwest through the graveyard to the ladder, climb it, then continue north and climb the next ladder.
Continue northeast to reach the bell tower. Unlock the gate, climb the ladder, and hit the bell with your melee weapon. This will turn the world to night — not just here in the cemetery, but on every level.
Jump down the ladder and head back the way you came just a bit to meet your first new friend. Don’t be scared, the pink ghosts just need your help! We need to guide them back to their statues — they will follow you slowly, but if you get too far ahead of them, they’ll give up and go back to where they started. Instead, I recommend hitting them with your weapon to get them to go the way you want. They won’t get hurt, don’t worry.
The first ghost needs to be brought just south of where you find it — jump down the ladder and look southeast, and you’ll see a statue that looks a lot like a tall, thin version of the ghost. Lead (or whack) the ghost into it, and it will enter the statue, giving it’s key-hole eye a pink glow.
From the first statue, go west, then south at the fork, and you’ll see ghost #2. Lead it southwest and down the stairs to find the second statue, then lead it in.
Continue southwest, then southeast when you reach the wooden sign, and cross over the long bridge. Go southwest again at the lever, and over the next long bridge. Take the elevator down, then head southeast to find ghost #3. Lead him further down the path to the first ladder, then go west from the first ladder until you reach the long ladder. Jump down and stand near the statue just to the east, and the third ghost should enter it.
Climb up the ladder, then go east and jump down the next ladder you come across. Continue east and climb the next ladder, then continue northeast and climb the next ladder. You’ll face your first (and only) night time enemy in the Lost Cemetery here. Take him out, then continue northwest across the bridge.
At the lever, head northeast across the small bridge to find ghost #4. Lead or hit this ghost further northeast, and you’ll quickly find its statue home.
You can skip this paragraph if you don’t care about getting 100% completion. Go southeast onto the small bridge, and halfway across the bridge, use your hookshot to reach the ankh just southwest of you. Keep hookshotting to the next ankh until you are above a secret passageway. Do a plunging attack to enter the passageway, follow it to its end, then exit and grab the Large Soul Mass. Drop down to the grass, then drop down again due east of where you just landed. Head northeast to climb the ladder, and then go northwest back across the bridge to the statue you filled with ghost.
Go southwest, back the way you came, and continue southwest down the stairs near the lever (passing under the large grey archway). At the bottom of the stairs, go northwest to find ghost #5. Lead this one northwest and then further north up the stairs, and you’ll quickly see his statue home.
Continue up the stairs, and you’ll find ghost #6. Jump down the nearby ladder and lead this ghost to one of the statues next to the ladder. Once you drop down, ghost #7 will probably start approaching, so lead the little fella to the last free statue.
Phew! Now, we’ve gotta find our way to that big ‘ole door we opened. Go southwest, all the way to the start of the level. Walk past the open door, and stand in the gap in the rocks west of the door.
Hookshot to the ankh there, then hookshot a few more times, and drop down among the tombstones. Head east a bit to find a Vitality Crystal shrine, then continue east and you’ll be able to cross a broken bridge and drop down to enter the large (and now open) doorway. Grab the Ancient Tablet of Knowledge inside!
If you haven’t grabbed all the secrets here yet, feel free to do so before you continue on. Fill any life-seed pots you haven’t planted a seed in, and get the Bomb and Bow upgrades if you haven’t done so. You can also go back to Part 2 of the walkthrough to check for secrets you might have missed in the Lost Cemetery.