All you have to do is get parents, librarians, and other supporters (over 18 years old) to "like" Jan Brett on Facebook. The contest goes until April, so you have plenty of time to plot your strategy.
In case this sounds intimidating, here is an encouraging word from the contest website: "In a previous contest a medium-sized school was the winner. The teachers and parents from the school went to all the nearby assisted living housing and asked the residents to help out by sending in entries." Have fun!