Find out how many batteries your LCD clock takes, and insert them into the battery compartment on either the bottom or the rear of the clock, whichever applicable. Many LCD clocks use two sources of power to operate -- one is a standard power cord that plugs into your wall, and the other is a set of regular batteries. In the event that the power goes out in your home, the batteries will keep the clock from turning off. This is especially valuable if you use the clock as an alarm.
Set the appropriate time on your LCD clock. Typically these LCD clocks will have either a "Time," a "Clock Set" or other similarly named button that you need to press to get this process started. With the aforementioned button held down, press the "Hour" button to adjust the hour on the front of the clock and the "Minute" button to adjust the minutes displayed on the front of the clock until the LCD clock reflects the current time.
Set the alarm on your LCD clock, if applicable. Once the proper time has been set, press the "Alarm" button on your clock -- typically located on the top or the front -- and set the appropriate hours and minutes using the "Hour" and "Minute" buttons you used to set the time. When you release the "Alarm" button the front of the clock will still reflect the current time, but an "Alarm" indicator light should be illuminated on the front of the device indicating that an alarm has been set.