Anyone who has sinned after receiving the Sacrament of Baptism, shall receive the Sacrament of Confession. Our good LORD knows our sins, but He wants us to know them also and confess them to a priest, who is the dispenser of the Blood of Christ. Nothing can take your sins away, but His precious Blood.
Before we go to Confession, of course we need to examine our conscience. Then go to the priest and confess all sins committed since the last good confession. To make a good confession, we must confess humbly, sincere, and entire.