If your Apple Pencil is unresponsive on your iPad in any of your apps, it is most likely out of battery. Depending on your model, you can charge your Apple Pencil in two ways:
Your Apple Pencil should be ready to use in a few minutes. Please make sure Bluetooth is on for your iPad.
If you still cannot use your Apple Pencil, you may need to repair the Apple Pencil to your iPad. To do so, follow these steps:
Once paired, you can now use the Apple Pencil with Duet, which turns your device into a high performance drawing tablet, extended display, or Remote Desktop. Learn more here!