After you have obtained the water medallion, head over to kakariko village. You will find sheik who will teach you the Nocturne of Shadow. This song will teleport you behind the graveyard into a cave where you must light a large amount of lanterns to open the door to the Shadow Temple. Use Din's fire to get all of them at once from the center.
Beat a boss and a chest will appear with a bow in it.
Go through the Shadow Temple, he is the boss.
Yes, She Shiek shows up in Kakariko during the shadow fight with Bongo Bongo(Shadow Boss).
You collect the Longshot in the room of the Water Temple after defeating the sub-boss, "Dark Link."
Play through the temple. You do know there are literally hundreds of walkthroughs on YouTube.
Barinade
In the Shadow Temple from a chest that appears after defeating the mini boss Dead Hand.
It is in the Fire Temple, on the 4th floor. Consult a strategy guide for more details. Naw, duh.l'v'l B-)
move around
If you're talking about dodongo's cavern, you fall down a hole. In the actual fire temple, then you jump onto the rock that has some holes on the ground.
Electrocute him.
Ghoma, took me 3 minutes :D