Jesus gives the great commission to his apostles that the Church accomplishes the work of evangelization, particularly in the area of faith formation. How is it that you come to know God?
Typically, an adult coming into the church participates in the Rite of Christian Initiation of Adults. RCIA is a period that may last some time, as a person is journeying with other Christians and those who are thinking about becoming Christian. They learn about Jesus and the Spirit that is coming into their life. The culmination of this period of preparation takes place at the Easter vigil where a person is received into the church, Baptized, and receives Holy Communion and Confirmation.
Very often, individuals who have perhaps received Baptism but not Communion or Confirmation will also participate in RCIA, receiving complete initiation at the Easter vigil. There are also those who are other Christians, people who were baptized in other communities but desiring to become Catholic. They too participate in the RCIA and finally receive Communion and Confirmation at the Easter vigil.