This may be of some help. From what I can tell kah22, you are expecting the bottom button to turn off your screen. I hope I am right. The bottom button is known as the home button and will only take you back to your home screen. The button on the side is known as the power/wake/sleep button and will turn your screen off and on (make it go black), and if you hold it, it will turn the phone off and on competely.
If you want to change your home screen, you can do this by pressing the bottom (home) button, and then with two fingers, pinch the screen by swiping the two fingers towards each other against the screen in a pinching motion. You will see all your home screens together, and the one you want to see first when you press the bottom button can be set by tapping the little house icon above it.
I hope this helps.