To teach the atonement I gave each girl a bag of sugar as a present just for coming to church at the beginning of the lesson. I told them just like they recieved a present from me for coming to church, everyone who has ever lived on the earth gets a present from Jesus Christ just for coming to the earth because of his atonement on our behalf. However, if we would like something better in the end, we need to work for it. Eternal life doesn't come without hard work and perserverence while here on earth. We need to keep the commandments, repent, etc. to gain celestial glory. This part of the atonement is conditional on what we do in our lifetime. At the end of the lesson is something much better than your bag of sugar, but to recieve it you must work hard during the lesson. Everyone who wants to recieve this extra special gift at the the end, must make at least one comment, read a scripture, or share a personal experience during the lesson, and your gift will be given to you at the end of the lesson. At the end of the lesson, reiterate that the Atonement was made for everyone, but only those who are willing to do what's necessary to gain eternal life will do so.