Lets' get back to the crown.
It should look like this.

After cutting the curve marks on the bottom
edge, apply a thin layer of glue.

Fold over and smooth as shown.
Notice how the side seam 
(soon to be the back seam)
has been clipped at the top?

Now start to curve the piece like a cone
shape and add a thin layer of
glue along the seam allowance.

Ta Da!  Here is your pointy Crown!
Be sure to smooth the seam down in back.

Here are the 2 finished pieces
of the witch's hat.
Pretty easy so far, huh?

Okay, I like to trim my brim opening
and keep test fitting it until
it slides over the crown 
and the bottom edges meet.
Yea, right now you are asking:
What are those clip marks 
for on the pattern?
If you want to glue it that way then 
you would fold them under to the
inside of the crown.  I like this
New way better.

See?  This is so much neater and easier!
Add a small line of glue on the
bottom edge of the crown and
slide the brim down over it until they meet.

LET THIS DRY A LITTLE
but not all the way if you are going
on to the next step.

You can paint the brim edges with black paint
if the leather is lighter on the inside

Personally I like a crinkled, worn,
hat full of character, not a straight up
pointy hat. 
It is easier to manipulate the 
leather if it is still damp.
Pull the back of the brim up.
Bend half of the front brim up and
the other half down.
Put your finger in the crown for support
pinch the tip of the crown and 
gently push it down causing it to crinkle
Play around with this until you are
satisfied with the look.
Let it dry!