Yes, you need to study if you want to be a religious education teacher. Each diocese has formation programs that vary according to the circumstances of each place. The commitment to teach the faith is very important and that is why initial and continuous formation are indispensable conditions for this important service in the life of the church. Each one of us is called to be a living stone in the building of the church (1 Pe 2:5) and to assume a service within the church is the best way to give witness to the fact that we are disciples of Jesus in our community, just as He has asked us to do (Mark 3:14).
Go to your parish and ask about the requirements for this service and make a commitment with joy!