How did the elves of the three fir trees in Zelda come out?

The steps to summon the three fir elves in Zelda are as follows.

1. Go to Hartno village, find the old man Hartno, talk with him and accept his task.

2. Collect ingredients and go to Potomac to cook delicious food on the stove.

3. Go to three fir trees, put the food on the altar next to the trees, and then wait for a while.

4. After completing the worship task, talk to the old man Hartno, and then go to three fir trees to see the elves appear.