When Sister Lucia Santos, one of the Fatima seers, received an apparition from Our Lady in 1925, she was a postulant with the Sisters of St. Dorothy in Tui, Spain. She explained that Mary wanted an act of reparation for the graves sins of modern humanity by telling Lucia: “Look, my daughter, at my Heart encircled by these thorns with which men pierce it at every 
moment by their blasphemies and ingratitude. You, at least, strive to console me, and so I announce: I promise to assist at the hour of death with the grace necessary for salvation all those who, with the intention of making reparation to me, will, on the first Saturday of five consecutive months, go to confession, receive Holy Communion, say five decades of the beads, and keep me company for fifteen minutes while meditating on the fifteen mysteries of the Rosary.”
Those who follow the Fatima prophecies believe that honoring Mary through Confession, receiving Jesus in the Eucharist, and praying the Rosary consoles the United Hearts of Jesus and Mary, who grieve for the suffering of the world caused by sin and apathy.
The three requirements are:
Sacramental Confession: Eight days before or after the first Saturday of the month, a penitent may make his or her confession but is not required to disclose the reason for the Sacrament as part of the First Saturday devotion. As with any confession, the penitent should approach the Sacrament with a sincere and contrite heart, intending to amend his or her life of sin and in making an entire confession without delay.
Receiving Holy Communion: In addition to Confession, a devotee should also receive Holy Communion within twenty-four hours of the actual first Saturday of the month – and should be done in a state of grace. Again, the intention does not have to be spoken aloud but should be a conscious and intentional act at least made as mental prayer to Our Lady and Jesus. Also, it is of note that the communicant does not have to receive as part of Mass, especially if conditions prevent him or her from doing so (a disability, inclement weather, no Mass offered, etc.). In the latter case, the recipient will need to explain to a priest who gives him or her Holy Communion the reason for receiving on that particular day as related to the First Saturday Devotion.
Reciting at least Five Decades of the Holy Rosary: When one offers up his or her Rosary on the first Saturday of each month, it should be for the intention of reparation of sin against the Immaculate Heart of Mary. In addition to the recitation of the Rosary, a fifteen-minute meditation on the Rosary is recommended for devotees, which can be done privately or in a group of others who share in this devotion. Because of the sins against Our Lady, such as blasphemous images or mockeries of her name and purity, the Act of Reparation is a gift one can bring to her through this meditation and by cleansing one’s soul of sin.
The Blessed Mother promised Sr. Lucia that the person practicing this devotion would receive many powerful graces, particularly at the hour of death and for one’s salvation.