Button at the top right side, small black, feels kind of grippy.
Push once and let the screen light up with the Apple logo in the center. Once that happens wait for the "slide to unlock" screen. If you've missed it, and it has gone dark again, just push the squared button on the front and then "slide to unlock."
You are free to move about the interface. To rearrange the icons, press and hold for 3 seconds until they wiggle, then press and drag to the desired location, and you can move them between pages too!
More support is available on Apple's website!