When did the Church appear?

[DanielM]

Well, it was certainly practiced to a preach in the mi 4th Century.
Athanasius of Alexandria said that "Just as a man is enlightened by the Holy Spirit when he is baptized by a priest, so he who confesses his sins with a repentant heart obtains their remission from the priest."

Also John Chrysostom knew of Confession to the Priest alone, acting as a representative of God when he wrote:
"Great is the dignity of priests. 'Whose sins you forgive,' He says, 'they are forgiven them' [John 20:23] The things that are placed in the hands of the priest, it belongs to God alone to give" (Homilies on John 86:4)

He mentions the Priest being there but the confession going to God alone, so it is safe to presume that this is a private form of confession in the mid 4th century also.