A: Yes, this can be done at the Rite of Acceptance (see RCIA 33.4, 73) or more commonly at the Preparation Rites of Holy Saturday. The Rite of Choosing a Baptismal Name, if it is done on Holy Saturday, follows the Recitation of the Creed, if it had not been previously celebrated at the Rite of Acceptance, according to the discretion of the diocesan bishop. The United States bishops have established “the norm that there is no giving of a new name… but approves leaving to the discretion of the diocesan bishop the giving of a new name to persons from those cultures in which it is the practice of non-Christian religious to give a new name” (RCIA 33.4; see also RCIA 73, 200-202). For other nations, the RCIA leader should check what is the norm regarding choosing a new Baptismal name. Candidates, who are already baptized, do not participate in this Rite. However, the Preparation Rites offer an appropriate time for both elect and candidates to announce the choice of their patron saints, and to explain briefly why the particular saint has been chosen.
Although not provided for in the Rite of Confirmation or in the RCIA ritual book, it has long been a custom in the United States, and perhaps other countries, to choose a patron saint for Confirmation, and to be confirmed under the name of this saint. Even though the ritual book does not mention adding patron saints for Confirmation to the Litany of Saints prayed at the Easter Vigil, provision for adding Baptismal names (see RCIA 221) suggests that this is not liturgically inappropriate. In the course of the initiation Mass itself, for those newly baptized and newly received, each godparent or sponsor places a right hand on the new Catholic’s shoulder and states the name of the candidate, as the celebrant approaches to confer the sacrament (see RCIA 235, 494, 591). It is especially appropriate to use the names of patron saints chosen by the newly-baptized and newly-received Catholics, a practice not specifically provided for in the ritual book but that may be provided for by the bishop in diocesan guidelines for celebration of Confirmation.
—Answered by William Keimig