Q: Apple Pencil does not write

Do you have an iPad Pro?  The Apple Pencil only works with the iPad Pro, not any of the older iPad models.

You first need to pair it.

Pair your Apple Pencil with your iPad Pro

The first time you use your Apple Pencil, take off its cap and plug it into the Lightning connector on your iPad Pro. When you see the Pair button, tap it.

• Apple Pencil works only with iPad Pro.
• If you turn off Bluetooth—for example, if you turn on airplane mode—you'll need to turn on Bluetooth and pair your Apple Pencil again.

Well, you cannot write or draw in email, so it won't do a thing there. In notes you can draw witht the drawing tool, but you cannot write in the text input field.  In notes, tap the little squiggly line in the lower right to enter drawing mode.

And? What happened?

Read here on what apps work with Apple pencil

http://www.imore.com/best-apps-drawing-ipad-pro-apple-pencil

Well, best you go to an Apple retail store and let Apple employee(s) show you how to use the pencil.

Let them also show you what apps to use.

You're welcome.