For the most part, this clock does not require anything other than initial setting. Once the clock is configured to your liking, you can simply set it down and it will run for many many years without difficulty.
The clock needs to be powered properly. Use only DC power adapters, 9VDC regulated is best but 9VDC unregulated work as well. Clock brightness may vary with adapter voltage and model. The adapter current should be between 150mA and 500mA for unregulated and 150mA + for regulated.
For the time backup battery, use a 3V lithium CR1220 coin cells (any 12mm 3V lithium will work fine such as 1216 or 1225 but 1220 is most common).
The clock can be set to either 12hr or 24hr mode. The time will display differently depending on which is set.
If the clock is in 12hr mode, then when it is a PM time, a dot will appear in the top left corner.
If you press the SET button while just displaying the time, the clock will briefly display the day and date.
The alarm is turned on and off by the slide switch. If the alarm is set to ON you will see a dash on the left of the clock display indicating that.
For example, here is the clock display with the alarm on:
When the alarm is ringing, you can go into 10-minute snooze by pressing any of the three buttons. The display will show the word Snoozing and then the time will be displayed but the dash will blink.
Every time you press a button, it will reset the snooze to 10 minutes.
When the alarm is ringing, you can turn it off by flipping the switch.