There are two ways to become Catholic.
- The main one is to join the Rite of Christian Initiation program at the parish nearest you, and join with others in the process of learning and preparation to make your profession of faith, be confirmed, and receive the Eucharist. This process culminates in Holy Week of next year, and probably begins in September. You can do this at your age, with your parents' permission, or when you are eighteen.
- The other way is to take instruction in the faith from a priest and enter the Church as an individual, rather than with the RCIA group at Easter. If you have been baptized in a denomination that uses the words,
"I baptize you in the name of the Father, the Son, and the Holy Spirit."
you do not have to be rebaptized.
You can pray to saints whenever you wish! I would start with the most important saint, Jesus' Mother, because she specializes in helping people come closer to Jesus.
If you wish to go deeper, in understanding what we believe as Catholic Christians, consider buying a cheap copy of the Catechism of the Catholic Church to learn all the basic teachings and beliefs.