Charging/program port uses a normal micro USB cable and USB charger.
The green LED tells you when it's fully charged.
Sliding switch turns it on and off. When you first turn it on, some random LEDs will light up, then there's a red LED inside that will blink a couple of times, then the LEDs will do a rainbow, then it will start the first image. The length of that rainbow also tells you how charged the battery is.
The button changes the image. If you hold the button down 5 seconds, the images will change every 15 seconds.