How can I go to the city of the sky?

Once you've found the 6 Statues and gone back to see Shad in Kakariko Village, Warp the Cannon to Lake Hylia and have the guy fix it!

After the temple of time (The place in the Sacred Grove) you need to reactivate the Dominion Rod by going to the hidden city in the north where you have to kill 20 moblins. Once the rod is fixed there are statues all around hyrule that should now be marked on the map. Move the statues from where they are standing and step into the light where they were. Once you have done this at each statue go to the house in Kariokari village (not how it's spelt I know, but can't remember how to spell it) where you can go to the underground basement part. One of your friends should be there, chat to him and then move the statue hes looking at. Then go into the room that you open and get your friend to leave. Teleport the cannon in the room to lake hylia and get the cannon man to do 'special repairs' then hookshot into the back of the cannon and you should get blasted to the city in the sky.

After the temple of time (The place in the Sacred Grove) you need to reactivate the Dominion Rod by going to the hidden city in the north where you have to kill 20 moblins. Once the rod is fixed there are statues all around hyrule that should now be marked on the map. Move the statues from where they are standing and step into the light where they were. Once you have done this at each statue go to the house in Kariokari village (not how it's spelt I know, but can't remember how to spell it) where you can go to the underground basement part. One of your friends should be there, chat to him and then move the statue hes looking at. Then go into the room that you open and get your friend to leave. Teleport the cannon in the room to lake hylia and get the cannon man to do 'special repairs' then hookshot into the back of the cannon and you should get blasted to the city in the sky.

Head to Kakariko village and talk to the village shaman, he will send you on a quest to find a statue. After this you will go to the hidden village and will need to clear out 20 enemies. Show the rod to the old lady who comes out, she will give you the sky book, show this to Shad (in kakariko) he will send you to fill it, after filling the book he will restore power to the rod, use it to move an owl statue which will take you to the Sky Cannon, warp it to Lake Hylia and pay the cannon man 300 rupees to fix it, then clawshot into the back of it to get to the city in the sky.