Okay well I dont think you can actually MAKE them sleep. You can turn off the lights and hey may fall asleep earlier than what they normally would but other than that the only way to MAKE them get up or go to sleep is change the time to what you want so they go to sleep, or wake-up whatever you want.
To change the time press ( b ) on the main screen so it shows the time then hold a+c together, so it should say SET, then click ( B ) twice so it goes to the clock setting then use (a) to change the hour. Then press ( B ) to go the minutes then use ( a ) to change minutes.
Hope that helped.