After completing Din's Silent Realm, you receive the Fireshield Earrings, which allow you to reach the Eldin Volcano Summit.
Reach the Summit
Go to the air vent that takes you to the top of the big slide. Instead of sliding down, go into the fiery room. The fireshield earrings will keep you from getting hurt. Go into the cave at the top of the ramp.
Extinguish the Flames
Past the bird statue, you can hop down and make your way past some enemies and Cursed Spumes in the lava. There is a light cave straight ahead. Go into it.
Use an empty bottle to collect some water from here. Then go back into the cave. Turn left and go into the dark cave here.
Talk to the Goron here and you will get the ability to dowse for Goddess Cubes. Then pour water into the frog statue to get rid of the flames.
Go past where the flames were. Use the clawshot to get up onto the vines and walk onto the small ledge above the statue. Pour water from an empty bottle into the frog's mouth.
In the next area, the Goron will say that you will need a large container to extinguish the flames here.
Go left from the door and run up to the open window. Use the clawshot on the vines. Kill the lizalfos and go ahead to reach a goddess cube.
Go back to the small pond where you got some water to pour into the frog statues. The Mogma here will tell you that the water source on Eldin Volcano is fed by Lake Floria. Fi tells you to visit the water dragon.
Get the Dragon's Basin
Go to Faron Woods and descend at the Floria Waterfall statue. While here, use the clawshots to climb the ivy to the goddess cube above the door into the cave.
Go into the cave and talk to the water dragon. Tell Fi to summon Scrapper to carry the basin.
Use the bird statue to return to the sky. Fly to Eldin Volcano. You will touch down at the base of the volcano. You have to protect the robot from the enemies as you make your way to the summit. Start by going left. Use arrows to kill the bokoblins. You will find more arrows than usual as enemy drops and from grass and digging spots, so don't be afraid to use plenty of arrows.
When you reach the shield moblin, you can use the beetle to catch a bomb near the entrance to the rupee game, then drop the bomb on the moblin to destroy its shield. Then kill the moblin.
You will have to run up the shields of the iron shield moblins in order to get behind them and kill them.
When you reach the entrance to the Earth Temple, go to the right. Eventually you will reach a couple of lizalfos in the cave. Be very careful not to let them hit the robot.
Finally, when you reach the frog statue, the robot will automatically pour the water in. Go inside to reach the Fire Sanctuary dungeon.