In Skyloft, you found out that you need to find the missing propeller in order to point both windmills at the Light Tower. Read the Sealed Grounds Part 2 section to find out how to reactivate the robot, Scrapper.
You can now get the Sacred Shield from the market. The potion lady has a new stamina potion (green) that temporarily makes your stamina last longer.
Clean Pipit's House
Go to Pipit's house. His mother will ask you to clean the house. Use the Gust Bellows to blow away all of the dust and cobwebs. (P.S. Try using the Gust Bellows on her. It's funny.) She will automatically tell you when the job is done. You will get five gratitude crystals and 20 rupees.
Get Pipit and Karane Together
Talk to the old lady in the Academy to learn that she has heard noise from the restroom at night. Go to a bed a sleep until night, then go to the restroom. Try to open the door to discover that it is locked. The ghostly voice inside asks for paper.
Sleep until morning and talk to Cawlin, who gives you a love letter to give to Karane.
You can probably give the letter to the restroom person, but I didn't try it.
Give the letter to Karane and tell Cawlin that you did it. Then tell Pipit. Then go back to Karane to see a cut scene. You will get five gratitude crystals from Pipit.
Get a stamina potion at the bazaar, then go to Fledge's room at night and give him the stamina potion.
Finish your Lumpy Pumpkin Tasks
Go to the Lumpy Pumpkin and talk to the guy behind the bar to be assigned the second task. Talk to Kina, the girl outside. You have to carry five pumpkins and keep them from falling. Walk slowly, and if the pumpkins start leaning to the side, walk in the direction that they are leaning in to make them straighten up again. Once you get close to the shelf in the storage room, Kina will say that the task is finished.
The guy behind the bar says that the next task needs to be done at night. However, you aren't allowed to fly away from Skyloft at night, so you have to sleep in a bed in the Lumpy Pumpkin. There are some beds to the left of the entrance.
Talk to the owner at night and he will ask you to do a duet with Kina. The people in the audience will wave their arms in the direction that you should strum the harp. Try not to be hasty. Otherwise, you might end up moving when they don't move. There are some points at which they quickly change arm position that you need to watch out for. Try not to strum too broadly, or else you might strum when you don't mean to.
The background music will include more instruments if you are doing a good job. The audience will have a better reaction at the end if you did well. If your performance is not satisfactory, you will have to try again. If Kina says that you did an acceptable job or better, you will be done with all of the tasks. The owner will give you a piece of heart. After you sleep in a bed you will see the new chandelier.
Find the Propeller
If you use dowsing while on Skyloft, you will see that the propeller is somewhere around the Eldin Volcano. You can also learn this from the fortune teller in the bazaar.
The propeller is close to the entrance to the Earth Temple, so when you dive down to Eldin Volcano, choose the bird statue near the Earth Temple. Walk left from the entrance to the temple and look down the slope. Remember to use dowsing if you are having trouble. You will see the propeller near the fallen wooden tower at the bottom of this slope. Slide down the slope and examine the propeller to have the robot take it to the sky.
Use the bird statue to go back to the sky. The robot will be flying behind you with the propeller. Go to Skyloft and run over to the broken windmill on the southeast side of the island. Kukiel's father will automatically fix the propeller for you.
Turn the Windmills to the Light Tower
Use the Gust Bellows on the propeller to rotate the windmill until it is pointing at the Light Tower. A blue light will light up on the back of the windmill when it's pointing the right way. Be sure to stop blowing the air after the light lights up, because otherwise it will go too far and you will have to spin it all the way around.
If you didn't rotate it already, go to the windmill on the southwest side of the island and point it at the Light Tower as well.
A platform will rise on the Light Tower. Climb up to the top of it. A sign here says to play the Goddess's Song. Stand in the circle and strum the harp. Strum in time with the pulsing circle and Fi will sing the song for you. The tower will shine a beam of light at the area of clouds in the northwest.