The Sacrament of Confirmation is performed in high school for members of the church who have already been baptized and have received First Commuion & First Reconciliation.  For adults becoming Catholic and joining our Church, this sacrament is a part of our RCIA (Rite of Christian Initiation for Adults) program.

Confirmation deepens our baptismal life that calls us to be missionary witnesses of Jesus Christ in our families, neighborhoods, society, and the world.  . . .  We receive the message of faith in a deeper and more intensive manner with great emphasis given to the person of Jesus Christ, who asked the Father to give the Holy Spirit to the Church for building up the community in loving service.

~from the United States Catholic Catechism for Adults

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.