John 17:21 That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us: that the world may believe that thou hast sent me.
This document discusses the process of entering into communion with the Catholic Church. Though the process may differ slightly according to parish, this document is designed to give you the basics of what you'll need to know to begin the journey. Are you called to communion with the Catholic Church?
RCIA, or the Rite of Christian Initiation for Adults is where both the baptized and unbaptized typically begin their familiarization with the Catholic Church, it's teachings and go through the three Sacraments which will complete this journey, Baptism, Confirmation, and Holy Eucharist. Anyone can attend RCIA and learn about what the Church teaches, from the Church itself, without obligation. RCIA is free.
Ask your local Catholic parish if they have an RCIA program, and they will let you know where you can attend RCIA. Alternatively, if an RCIA program is not available, you may be given personal instruction by a Priest &c.
Familiarizing yourself with the teachings of the Church is a central component of becoming Catholic. This can be done a number of ways, though in addition to the above, I would suggest reading Sacred Scripture (with a solid Catholic Commentary) and the Catechism of the Catholic Church, which is the culmination of 2000 years of Church interpretation regarding the former. The New Testament can be read in it's entirety within the scope of about a month if you dedicate 30 minutes a day to study. Familiarization with the Order of the Mass is also integral. These things can give you a nice primer for when you begin RCIA.