What does having divine authority really mean? The authority to act in the name of God is called the priesthood. Some mistakenly think it gives one the power to tell other people what to do. What it actually means is that a person can act in God’s name in behalf of His church — like when we give someone power of attorney so they can act in their behalf.
Prior to the organization of The Church of Jesus Christ of Latter-day Saints, Joseph Smith received priesthood authority at the hands of John the Baptist, Peter, James, and John who received that same “power and authority” from Jesus Christ Himself ( Luke 9:1 ). These men appeared as angels and bestowed the priesthood upon Joseph Smith. The prophet today, Thomas S. Monson, is the authorized successor to Joseph Smith. He and the Church’s other Apostles trace their priesthood authority back to Jesus Christ in an unbroken chain of ordinations.
Talk Source: http://mormon.org/restoration
