For us, the first step to repentance is getting down on our kneeds and asking God to forgive us. At that point, if we are sincerely repentant, we trust in His grace to keep us and save us. But we must then follow through on our repentance and confess our sins to God before the priest and receive the absolution from the priest who has received the Holy Spirit in a special way from the bishop, who received Him from the bishops before him, back to the Apostles who received Him from Christ when He breathed upon them, ordaining them Apostles. When He did that He said that whatever sins the lose or bind on earth are losed or bound in Heaven, He was instituting the Sacrament of Reconciliation, graciosly offering us the forgivenines of our sins. This forgiveness is by the blood of Christ. In the OT the person confessing would have thier sins transfered to the offering which would be slain in thier place, by placing thier hand on it and confessing before the priest. In the NT we confess our sins before the preist, and our sins are taken from us. At the start of the Liturgy, the priest rubs his hands over the bread which will become the Body, and our sins are transfered to it. When the Holy Spirit comes down and makes it the Body and Blood, it is not a resacrifice, but a participation of the Sacrifice at Calvery which was one and sufficient, so in that way our sins are put upon Christ on the Cross, who bears our sins lovingly, dying for our sins.
The washing of the feet was also instruction about confession, Christ told St. Peter that he didn't have to be washed again (baptism), only have his feet wipped (confession), but that thhat must be done or he has no part with Him. He then told them (the Apostles who He ordained, not all) to do the same for each other, washing each other's feet.
This is the system that God established to give us the forgiveness of our sins. It is a fulfillment of the OT system of sacrifices.