The other guides are excellent, but rather outdated because of the new tutorial. So I hope that this helps with the
NEW TUTORIAL WORLD. (7-2-2017)
As stated elsewhere, you need 1 apple and 8 gold BLOCKS. Luckily, the gold blocks are more common than apples in the tutorial world.
You can either make an iron pickaxe, or pick one up in the Redstone area. If you go into the Redstone area, turn left and go down the stairs to the chest. There's a handy iron pickaxe for you there.
Now you're going to need the blocks. There's one near the Elytra, but the other 7 are going to need to come from the towers. Grab your pickaxe and climb the towers.
The hardest part for me seems to be the apple. Luckily, there's one right near the tutorial village. Across the pond, inside the mine cart track, is another little village. Go to the building with the lava in front. Inside is a chest with apples in it. The coordinates are:
X: -99
Y: 86
Z: -41
Then take your ingredients, make your Notch Apple (which still says "Golden Apple") and eat it.