Oracle of Ages
"You got the Graveyard Key!"
In Oracle of Ages, the Graveyard Key is needed to enter the east end of Yoll Graveyard, where the first dungeon of the game, the Spirit's Grave, is located. The Graveyard Key is found in a cave thats entrance is found under a tree in the south end of the graveyard. On the left side of the barrier, Link can burn the bottom tree with Ember Seeds. He can then enter the grave and light the two torches to acquire the Graveyard Key.
The Minish Cap
In The Minish Cap, the Graveyard Key is given to Link by Dampé in the Royal Valley. However, as soon Link walks outside of Dampé's house, a bird will come and steel it from him. Link can recover the key by killing the bird in the same area. Link can then access the Graveyard.