To charge your V3i battery, simply unscrew the tank or cartomiser, and then screw your battery into your 5v V3i charger. Plug the charger into a suitable wall adaptor or the USB port on your PC and laptop. You'll know when the battery has finished charging as the light on the charger will change to a solid green.
If you are using a wall adaptor, make sure that it is 1.5amp or lower, as a higher amp (such as fast-charge adaptors which come with some mobile phones) will be too powerful.
If you are using the Portable Charging Case, screw your battery into the charging port inside the case, and then hold the button on the back of the case for a few seconds until the charging lights come on. These will flash red and count up when your battery is charging, and then stay solid red to indicate when your battery has finished charging.