Plug the USB-C end of the cable into the charging base. Plug the other end of the cable into a USB-A power source, like your Surface. Place your pen in the charging base. Wait for a moment ...
For the cost of a common PDC004 Power Delivery “trigger” module and a bit of PETG filament, you can add yet another device to the list of things that work with your shiny new USB-C charger.