i need more information about the issue...how old is the baby? i wouldn't expect through the night sleeping until at least 6months. and every time there is a growth spurt the sleeping routine changes. but really i cant really give you more help until i know more info.
Without more info I'm going to have to tell you: Place baby on their back, in their crib/bassinet while either drowsy or fully asleep. Depending on the age of the baby "through the night" might mean 4 hours or 8-10 hours.