Apple Pencil for iPad air2

iPad Air2 does not support Apple Pencil - as the Air2 lacks the screen hardware with which an Apple Pencil interacts with iPad.

Here is the definitive compatibility list for Apple Pencil and iPad:

Apple Pencil compatibility - Apple Support

As your iPad does not support Apple Pencil, your options are limited. As an alternative, you might use a passive stylus (of which there are many to be found in Amazon), but these provide no more functionality than your fingertip.

If you want to use Apple Pencil, you’ll need to replace your iPad with a more recent model. All current models of iPad (the iPad9, mini6, Air4 and iPads Pro) support Apple Pencil.