To charge AXS and eTap AXS derailleur batteries, remove the battery from the derailleur and charge it on the AXS battery charger. These derailleur batteries are easy to remove without any tools.
The charger connects to the power source with a USB cable. The power source can be a USB port on a computer, but A/C home power adapters will also work!
For information on battery removal, installation, and charging, see the video SRAM Road AXS | How to: Charge AXS batteries.