Now that you know the prayers of the rosary, you will need to know the mysteries.
There are 20 mysteries, which are events in the life of Jesus and/or Mary, taken from scripture; or events concerning Mary taken from the Tradition of the Catholic Church, of which there are two. The mysteries are divided into 4 sets of 5 and a set of five mysteries is usually what is meant when speaking of 'praying a rosary'. Traditionally, there have been 3 sets of mysteries, with the fourth set added by Pope John Paul II in 2002.
The rosary has been called a summary of the Gospel, since it traces the Gospel story from beginning to end, and you will notice the chronological order of the mysteries. The addition of the Luminous Mysteries, the public life of Jesus from his baptism to the last supper, rounded out this Gospel summary.
The purpose of the mysteries is to have something to meditate on during prayer, and this meditation is an intergal part of the rosary. Without this meditation, the rosary becomes, in the words of Pope Paul VI, "...a body without a soul, and its recitation runs the risk of becoming a mechanical repetition of formulas, in violation of the admonition of Christ: 'In praying do not heap up empty phrases as the Gentiles do; for they think they will be heard for their many words' (Mt 6:7)."
The mysteries are Joyful, Luminous, Sorrowful and Glorious.
1. The Annunciation
2. The Visitation
3. The Nativity
4. The Presentation of Jesus
5. The Finding of Jesus preaching in the Temple
1. Jesus' baptism in the Jordan
2. The wedding feast at Cana
3. The proclamation of the Kingdom
4. The Transfiguration
5. Institution of the Eucharist
1. The Agony in the garden
2. The Scourging
3. The Crowning with thorns
4. Carrying the Cross
5. The Crucifixion
1. The Resurrection
2. The Ascension
3. The Descent of the Holy Spirit
4. The Assumption of Mary
5. The Crowning of Mary Queen of Heaven and Earth
Next: Putting it all together-- the prayers and the mysteries combine to make the rosary.
Apostolic Exhortation Marialis Cultus (2 February 1974), 47: AAS (1974), 156.
Apostolic Letter Rosarium Virginis Mariae (16 October 2002)