Couples are expected to participate in the required marriage preparation programs. In order to allow sufficient time to carry out the various steps of the program, couples must contact one of the priests at least six months prior to the anticipated time of their wedding.
MARRIAGE: A covenant or partnership of life between a man and woman, which is ordered to the well-being of the spouses and to the procreation and upbringing of children. When validly contracted between two baptized people, marriage is a sacrament (Matrimony) (1601).
Source - Catechism of the Catholic Church