No. 1285, pages 325-326 and no. 1315, page 333-334 of the Catechism of the Catholic Church: The Celebration of the Christian Mystery; Libreria Editrice Vaticana: Urbi Et Orbi Communications:
Baptism, the Eucharist, and the sacrament of Confirmation together constitute the "sacraments of Christian initiation," whose unity must be safeguarded. It must be explained to the faithful that the reception of the sacrament of Confirmation is necessary for the completion of baptismal grace.
"Now when the apostles at Jerusalem heard that Samaria had received the word of God, they sent to them Peter and John, who came down and prayed for them that they might receive the Holy Spirit; for it had not yet fallen on any of them, but they had only been baptized in the name of the Lord Jesus. Then they laid their hands on them and they received the Holy Spirit" (Acts 8: 14-17).
From the Baltimore Catechism No. 2; Benziger Brothers, Inc. and Tan Books and Publishers, Inc. No. 330, and No. 3, No. 671, page 139.
Q. What is Confirmation?
A. Confirmation is the sacrament through which the Holy Ghost comes to us in a special way to enable us to profess our faith as strong and perfect Christians and soldiers of Jesus Christ.
Q. When was Confirmation instituted?
A. The exact time at which Confirmation was instituted is not known. But as this Sacrament was administered by the Apostles and numbered with the other Sacraments instituted by Our Lord, it is certain that He instituted this Sacrament also and instructed His Apostles in its use, at some time before His ascension into Heaven.