how do i keep my parakeets warm to prevent death during the winter?

I have two parakeets that my 2 yr. old daughter begged and cried for last time were were in the store. everyday she talks to them and tells them to eat and sleep. she loves them so much i myself have started to like them as well. Being this the first time that I am caring for two parakeets, I want to make sure they make it through the cold winter. What should I do to keep them from dying? Thank you in advance.