The Active step screen will show number of steps taken. Notice the little person on the left of the screen. That indicates that the step sensor is active and will count steps.
If you don't see a person on the left of your screen, the step sensor is paused. See how to activate step sensor.
If you see a small Day 1 just to the right of the number, you are viewing the memory log screen and not the active step screen.
The Step screen can be found right after the clock. Press the MODE button until you arrive at the clock, then once more to get to the Active Step Screen.
The pedometer is designed to have the screen on all the time, it won't use any more power than a digital watch when idle.
To advance from one screen to the next, press the MODE button.