If you are already baptized you will have to make a general confession of all sins of your past life before Confirmation and first communion and profession of faith. You will be formally prepared for this during your class sometime, but there is nothing to prevent you from doing this earlier. If you want help in preparing, there are all kinds of links here on earlier threads which ask your same question. search confession or penance on the liturgy and sacraments forum, or search the evangelization forum for questions about RCIA itself. Simply tell the priest you are preparing for confirmation and this is your first confession.
