How do I know when my apple pencil is charged?

The first generation Apple Pencil, compatible with your new iPad10, does not incorporate magnets with which to dock with the frame of your iPad. Only the second generation iPad is designed to magnetically attach with the inductive charging dock of compatible models of iPad.

You can access the current charge status of your Pencil from iPad settings:

Settings > Apple Pencil

You can also monitor the battery status of both your iPad and Pencil using the Battery Widget:

Add a Batteries widget to your Home Screen

1. Touch and hold the Home Screen background until the apps begin to jiggle.
2. Tap “+” at the top of the screen, then tap Batteries.
3. Swipe left and right through the Battery Status widgets to view the size options.
4. The different sizes show different information.
5. When you see the size you want, tap Add Widget, then tap Done.

See Add widgets on iPad.

More information about charging your Apple Pencil can be found here:

Charge your Apple Pencil and check the battery - Apple Support

Wondering which Pencil you have.

Apple support have an article online that can help you... read the section that refers to your particular pencil.

Charge your Apple Pencil and check the battery – Apple Support