The Order of Christian Initiation of Adults is the Church’s process for introducing adults to Catholic faith and sacramental life. You may also hear its former English name, RCIA.
A little more context
Preparation involves learning, prayer, conversion and participation in a parish community. A person who is already validly baptized is not baptized again. The right pathway and timing depend on the person’s background; the parish should help distinguish preparation for Baptism from reception into full communion.
A practical beginning
Contact a nearby Catholic parish and ask to speak with its initiation coordinator. You can begin with questions and an introductory conversation. Tell them about any previous baptism and obtain a record if one is available.
Source & further reading
USCCB: Christian Initiation of Adults (opens in a new tab)↗Teaching summaries are introductions. Follow the linked Church source for its fuller context.