Those not already baptized Christians:
Becoming a Catholic is first and foremost about developing a relationship with Jesus Christ and living that relationship within the tradition of the Catholic Church. The Church receives new members through a process called the Rite of Christian Initiation of Adults, or RCIA.
Prior to beginning the RCIA process, an individual comes to some knowledge of Jesus Christ, considers his or her relationship with Jesus Christ and is usually attracted in some way to the Catholic Church. For some, this process involves a long period of searching; for others, a shorter time. Often, contact with people of faith and a personal faith experience lead people to inquire about the Catholic Church. After a conversation with a priest, or RCIA director, the person may ask to become a baptized member of the Catholic Church. Those making such a request are called “catechumens” and the time of prayer and learning is called the “catechumenate.”
The Catechumenate can last for as long as several years or for a shorter time. It depends on how the person is growing in faith, what questions they encounter along the way, and how God leads them on this journey. During this time, the catechumens consider what God is saying to them in the Scriptures, what changes in their life they need to make to respond to God’s inspiration, and what Baptism in the Catholic Church means. When a Catechumen and the priest and the parish team working with him or her believes the person is ready to make a faith commitment to Jesus in the Catholic Church, the next step is the request for baptism.
Baptism of adults is usually celebrated at the end of the season of Lent during the Easter Vigil, the evening before Easter Sunday, when the catechumen is baptized, confirmed, and, for the first time, joins fellow Catholics in receiving Holy Communion, the Eucharist.
Those already baptized in a Christian community:
When a bapatized Christain seeks to become a Catholic we call the process, “entering into into full communion with the Catholic Church.” In most cases, these individuals make a profession of faith but are not baptized again. To prepare for this reception, the people, who are called “candidates,” usually participate in parts of the RCIA to help them understand and experience the teachings and practices of the Catholic Church. Candidates may be received into “full communion” at any time.