How do you add your Apple Pencil

There are no technical means by which a mislaid Apple Pencil can be located. Even if still charged, a motionless Pencil will shut-off its Bluetooth connection to save power. Also consider that your Apple Pencil has neither a network connection, nor GPS capability, with which to be remotely located.

The only method to locate a lost Pencil is the Mark1 eyeball.

You don't. Apple Pencil cannot be tracked on Find My.