"In the Western Church the sacrament is usually administered by the bishop. At the beginning of the ceremony there is a general imposition of hands, the bishop meantime praying that the Holy Ghost may come down upon those who have already been regenerated: "send forth upon them thy sevenfold Spirit the Holy Paraclete." He then anoints the forehead of each with chrism saying: "I sign thee with the sign of the cross and confirm thee with the chrism of salvation, in the name of the Father and of the Son and of the Holy Ghost." Finally, he gives each a slight blow on the cheek saying: "peace be with thee". A prayer is added that the Holy Spirit may dwell in the hearts of those who have been confirmed, and the rite closes with the bishop's blessing." [source]

Confirmation can be conferred only on those who have already been baptized and have not yet been confirmed. As St. Thomas says:

“Confirmation is to baptism what growth is to generation. Now it is clear that a man cannot advance to a perfect age unless he has first been born; in like manner, unless he has first been baptized he cannot receive the Sacrament of Confirmation (Summa Theologiæ III.72.6).”

Confirmation imparts:

1. an increase of sanctifying grace which makes the recipient a "perfect Christian";
2. a special sacramental grace consisting in the seven gifts of the Holy Ghost and notably in the strength and courage to confess boldly the name of Christ;
3. an indelible character by reason of which the sacrament cannot be received again by the same person.