I actually found this part of the game
extremely fun.
I wish I never saved after getting it because I absolutely love doing this side quest.
You don't actually need the Big Goron sword to progress through the game, however some battles are much easier with it.
Since you've already got the prescription, you're one step closer, however I'm going to explain the steps from the beginning so other people who may come accross this thread can see how it's done.
PREP: - Must be adult Link.
- Must have Epona.
- Should have Suns Song.
PLEASE NOTE: You cannot use warp songs throughout this sidequest.
Using a warp song will cause the timer to run out and you will have to begin all over again.
THE QUEST BEGINS: Go to Kakariko Villiage and talk to the cucco lady.
She will give you a "Pocket Egg." You can either go outside and wait a day, or you can play the
Sun's Song to make time go by faster. Once it hatches, you need to go find Talon (you remember that guy who you had to wake up at the castle right? Well he's in the first house you see when you enter Kakariko) and wake him up using the "Pocket Cucco."
After he's awake, you need to go back and talk to the cucco lady again.
This time, she will give you a
Blue Cucco named, Cojiro. He doesn't crow. ):
You need to go to the Lost Woods now. You are able to use a warp song here if you so choose, or you can use Epona to get to Kokiri Forest.
Enter the Lost Woods and take the very first left turn. You should see a guy sitting there (he should look familiar, he's the carpenters son who sits at the base of the tree in Kakariko). Show him Cojiro.
After that's done, the guy will give you a mushroom.
You will have
three minutes to get from the Lost Woods and back to Kakariko Village. You'll need to talk to the "hag" behind the potion shop. If it's night, don't worry. The hag's shop will still be open. It will just be a matter of getting to her side which can be done using the hookshot or longshot and jumping on rooves.
She'll give you an odd potion which you have to take back to the guy in the Lost Woods.
You won't find him, instead you'll find one of the Kokiri girls who demands you give her the potion. She gives you a saw.
With the saw, you need to go to Gerudo Valley and talk to the head carpenter.
Spoiler: If you haven't beaten the fortress yet, the bridge will still be broken. You can use the longshot to get across or you can use Epona to jump across.
click to reveal
After you've talked to the carpenter, he'll give you a broken sword.
Now we have to climb up Death Mountain. You're not timed here.
Once you get to the stop of the mountain (the VERY top), there will be a huge goron up there. And I mean HUGE.
He'll tell you he can fix the sword, but you need to get him his eyedrops first.
Now you have the prescription (which is where OP is at).
Take the prescription to Zora's Domain and talk to the king.
He'll give you an Eyeball Frog. You need to take the Eyeball Frog to the labratory in Lake Hylia. You are given
three minutes to get from up the mountain to the lake.
After you talk to the scientist, he'll make the eyedrops and you will have
four minutes to make it from the lake to the top of the mounain.
After you give him the eye drops he will give you a claim check.
You then have to wait three days (which is where the suns song comes in handy). Show him the claim check after three days are up and he will give you the sword.