Baptism is necessary before one can receive any other sacrament. It is the first sacrament of Christian initiation which is completed with the sacraments of Confirmation and the Holy Eurcharist.
Baptism was instituted by Christ when he was baptized by St. John the Baptist, and when he commanded his apostles to go and baptize all nations in the name of the Father, and of the Son, and of the Holy Spirit. (Matt. 28:19)
Baptism removes all original sin: original sin and any other sins.
Baptism also makes us children of God, members of Christ, members of the Church, and heirs to the kingdom of heaven.
[From Outlines of the Catholic Faith: Teachings, Beliefs, Practices, Prayers, The Leaflet Missal Company, St. Paul, MN, 2011.]
The Sacrament of Baptism is available by appointment.