The Encyclical was published un June of 2015. Since then, people all over the world have studied Pope Francis' encyclical on the Care for Our Common Home, the Earth. Inspired by his namesake, St. Francis of Assisi, Pope Francis entitled the document using the first words of St. Francis' Canticle of the Sun, "Praise be to you, my Lord!" which is the translation of the words, "Laudato Si'".
You can download a free PDF of the Encyclical or buy a bound book of Laudate Si' from the United States Conference of Catholic Bishops or from Amazon or other booksellers.
The Encyclical is grounded in Catholic Social Teaching, outlined in the Catholic Catechism and the Pontifical Council for Justice and Peace. Here is a short summary presentation of Catholic Social Teaching (CST)