Both our standard 510 EGO and Twist batteries charge in the same way.
First, unscrew your tank from the battery and then screw it into your 4.2v USB Charger. Next, plug the USB end of this charger into a USB port on your PC or laptop, or into a 5v USB to Mains Adapter which can then be plugged into the wall.
The light on your charger will be red, and occasionally flash green. Then, when your battery has finished charging, it will be a solid green.
When charging your 510 EGO or Twist battery, be sure to only use genuine JAC chargers and suitable 5v wall adaptors ('Fast-charge mobile phone adaptors are not suitable), and don't leave your battery charging unattended.