1 Upon you my fellow servants, in the name of Messiah I confer the Priesthood of Aaron, which holds the keys of the ministering of angels, and of the gospel of repentance, and of baptism by immersion for the remission of sins; and this shall never be taken again from the earth, until the sons of Levi do offer again an offering unto the Lord in righteousness.
Imagine the joy that Joseph and Oliver must have felt when they were given the priesthood power. Joseph had long wondered about his state with God and what he would need to do to be saved. That same inquiry led him to his knees and led to the first vision. That same inquiry about baptism led them out to the woods to pray. And now, an angelic being appeared and bestowed on them priesthood authority to baptize unto repentance.
I love the idea that the priesthood holds keys for the Gospel of repentance. While people have repented and been forgiven without priesthood on the earth, the priesthood provides a god sanctioned conduit for divine repentance. It allows us to make our repentance manifest through the ordinance of baptism. Therefore, the Aaronic priesthood is intimately connected to the Doctrine of repentance.