"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 to 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. They they laid their hands on them and they received the Holy Spirit" (Acts of the Apostles 8:14-17).
Confirmation perfects Baptismal grace; it is the Sacrament which gives the Holy Spirit in order to root us more deeply in Christ, strengthen our bond with the Church, associate us more closely with her mission, and help us bear witness to the Christian faith in word and deed.
Confirmation, like Baptism, imprints a spiritual mark or indelible character on the Christian's soul; for this reason one can receive this Sacrament only once.
In the Eastern Rite Churches Confirmation is administered immediately after Baptism, and is followed by reception of the Eucharist, highlighting the unity between these three Sacraments of Initiation. However, in the Latin Rite, including the Roman Church, Confirmation is administered when the age of reason is reached. Baptismal promises are renewed, expressing the connection of the Sacraments. Confirmation is ordinarily reserved to the bishop, emphasizing the strengthening of the bond to the Church.
The essential rite of Confirmation is anointing the forehead of the baptized with sacred chrism, together with the laying on of the bishop's hands and the words: "Be sealed with the gift of the Holy Spirit."
To learn more, see The Catechism of the Catholic Church, paragraphs 1285-1321.
Preparation for the Sacrament of Confirmation is a two-year process. Children preparing to be confirmed must attend religious education classes at the parish on a regular basis one year prior to the year in which the Sacraments will be received. Sacramental preparation is a collaboration of parents (as primary teachers of their child), catechists, and the faith community as experienced in the Sunday liturgies.
Adults seeking to be confirmed, see Becoming Catholic / RCIA