The couple should approach their parish priest, and arrange with him for their marriage to be witnessed, celebrated, and registered in the Church. This is a step which is strongly encouraged.
In publicly witnessing to Christian marriage as an indissoluble and faithful covenant that is open to children, such couples assist in evangelising the wider culture. In making such a declaration before God and his Church, couples invoke the grace they need to live their vocation and publicly profess not only their love, but also their faith and hope.
If a couple has married outside the Church, and at least one spouse has been married before, they will need to determine with the help of their parish priest, or of a Church tribunal, whether it is possible for their marriage to be blessed by the Church. In some cases the process will be straightforward, in others it may take longer.
In both of these situations, a word of caution is in order. It is not uncommon for couples to seek to have their marriages recognised by the Church, right at the time when they are experiencing difficulties in their marriage. The Church’s blessing can seem to offer a quick fix for the strains in a relationship.
A priest should therefore take time with the couple to ensure that a sacramental marriage in the Church, with all its implications, really is the right step for them to take at this time. There may be a need for a sensitive pastoral response involving further spiritual and catechetical formation pertaining to the understanding of marriage and of its true vocation and mission.