When the Kindle is first switched on, you'll be presented with a tutorial. In case you missed it and want to have a refresher, here is the tutorial again.
(Note: the Kindle below is a 2012 Paperwhite. The 2013 model is different as the lighting is much more even and there are no 4 points of light visible at the bottom.)
You may also swipe left or right anywhere to turn pages.