You need first to set your own unlock pattern by connecting some of the nine white dots together (There is a default unlock pattern pre setted). When you try to unlock your phone, you need to draw the same pattern exactly as you set.
You can also protect your side bar slider key -- double click the menu key to lock the phone. When the phone is locked, single click the menu key to show you the lock screen with large time display, if you only want to glance at the time, signle click the menu key again to turn off the light to save the battery!
The lock screen can be easily configured according to your own preference: you can download plenty of backgrounds for free, the date and time display can be changed, the color of the text is also configurable.