You see how it has a usb plug and a plug for your iPhone? You take the USB plug and plug it into a computer or a wall charger with a USB port in it to charge the battery pack. The light will turn green that it is full. Then you hold onto it and just move the cap covering the iPhone plug and plug it into the bottom of your phone to charge it 50%! It really is handy to have. And the battery pack will hold the charge for a month or so. There is a battery button on the side you can push and the light in the front will indicate if the battery is full or if it needs charging. Hope this helped! (: