In its present form the custom of displaying figures depicting the birth of Jesus Christ owes its origin to St. Francis of Assisi, who made the Christmas crèche or manger for Christmas Eve of 1223.
Consider blessing your Nativity Scene with the following prayer from the Book of Blessings:
"God of every nation and people, from the very beginning of creation you have made manifest your love: when our need for a Savior was great you sent your Son to be born of the Virgin Mary. To our lives he brings joy and peace, justice, mercy, and love. Lord, bless all who look upon this manger; may it remind us of the humble birth of Jesus, and raise up our thoughts to him, who is God-with-us and Savior of all, and who lives and reigns for ever and ever. Amen."
Christmas Tree
The use of the Christmas tree is relatively modern. Its origins are found in the medieval mystery plays that depicted the tree of paradise and the Christmas light or candle that symbolized Christ, the Light of the world. According to custom, the Christmas tree is set up just before Christmas and may remain in place until the Solemnity of Epiphany.