It's rather simple: when there is occasion to procure a dispensation that exceeds the powers of the ordinary, or when there are special reasons for direct recourse to the Holy See, procedure is by way of supplica (petition) and private rescript. The supplica need not necessarily be drawn up by the petitioner, nor even at his instance; it does not, however, become valid until he accepts it. Although, since the Constitution "Sapienti", all the faithful may have direct recourse to the Roman Congregations, the supplica is usually forwarded through the ordinary (of the person's birthplace or domicile, or since the Decree "Ne temere" the residence of one of the petitioners), who transmits it to the proper Congregation either by letter or through his accredited agent; but if there is question of sacramental secrecy, it is sent directly to the Penitentiaria, or handed to the bishop's agent under a sealed cover for transmission to the Penitentiaria. The supplica ought to give the names (family and Christian) of the petitioners (except in secret cases forwarded to the Penitentiaria), the name of the Ordinary forwarding it, or the name of the priest to whom, in secret cases, the rescript must be sent; the age of the parties, especially in dispensations affecting consanguinity and affinity; their religion, at least when one of them is not a Catholic; the nature, degree and number of all impediments (if recourse is had to the Congregatio de Disciplinâ Sacramentorum or to the Holy Office in a public impediment, and to the Penitentiaria at the same time in a secret one, it is necessary that the latter should know of the public impediment and that recourse has been had to the competent Congregation).