The Catechism of the Catholic Church teaches that Baptism makes one a member of the Body of Christ and prepares one for the reception of the other sacraments. The Eucharist gives one the "food of eternal life" (John 6:54) and allows one to have communion with Jesus and our brothers and sisters in Christ. In the Sacrament of Confirmation, the baptized person is “sealed with the gift of the Holy Spirit” and is strengthened for service to the Body of Christ.
The effects of Confirmation bring an increase and deepening of baptismal grace:
If you are an adult who has been Baptized and received your Holy Communion, catechized, but have not been Confirmed, then you are a candidate for the Adult Confirmation classes.