Aieno, the power to forgive sins was granted to the apostles by Christ himself.
The plain reading of the Scripture is that the apostles specifically are given the power to forgive or retain sins. An important part of Jesus’ commission was to forgive sins. This commission is passed on to the apostles.
How can they forgive sins, unless individuals tell them what their sins were? There is thus, for those who want to be forgiven sins, a necessity of declaring their sins to the apostles, and it is up to the apostles, to either forgive or retain their sins.
That is what the sacrament of confession does.
Peace