From the 1983 Code of Canon Law, canon 892:
“As far as possible ther person to be confirmed is to have a sponsor. The sponsor’s function is to take care that the person confirmed behaves as a true witness of Christ and faithfully fulfils the duties inherent in this sacrament.”
(Code of Canon Law: Latin-English Edition, Canon Law Society of America, 1995, ISBN 0943616204. Another translation can be looked up at
vatican.va/archive/ENG1104/_INDEX.HTM ).
From the Introduction the the Rite of Confirmation:
“5. As a rule there should be a sponsor for each of those to be confirmed. These sponsors bring the candidates to receive the sacrament, present them to the minister for the anointing, and will later help them to fulfill their baptismal promises faithfully under the influence of the Holy Spirit whom they have received.”
(The Rites Volume One, Liturgical Press, 1990, ISBN: 0-8146-6015-0, page 480).
The sponsor’s role in the ceremony, as described in the Rite of Confirmation (within Mass):
“PRESENTATION OF THE CANDIDATES
21. After the gospel the bishop and the priests who will be ministers of the sacrament with him take their seats. The pastor or another priest, deacon, or catechist present the candidates for confirmation, according to the custom of the region. If possible, each candidate is called by name and comes individually to the sanctuary. If the candidates are children, they are accompanied by one of their sponsors or parents and stand before the celebrant.
If there are very many candidates, they are not called by name, but simply take a suitable place before the bishop.
HOMILY OR INSTRUCTION …”
After the homily the candidates stand and answer questions. The bishop prays over them. Then:
“THE ANOINTING WITH CHRISM
26. The deacon brings the chrism to the bishop. Each candidate goes to the bishop, or the bishop may go to the individual candidates. The one who presented the candidate places his right hand on the latter’s should and give the candidates name to the bishop; or the candidate may give his own name.
27. The bishop dips his right thumb in the chrism and makes the sign of the corss on the forehead of the one to be confirmed, as he says:
N., be sealed with the Gift of the Holy Spirit.
The newly confirmed responds:
Amen.
The bishop says:
Peace be with you.
The newly confirmed responds:
And also with you.”
Who puts their right hand on the candidate’s shoulder? From n. 21 the one who presents is the “The pastor or another priest, deacon, or catechist present the candidates for confirmation, according to the custom of the region.” But from n. 5: “These sponsors bring the candidates to receive the sacrament, present them to the minister for the anointing …”. A little confusing. I thnk it can be interpreted both ways. The practice I have seen is that the sponsor puts his or her right hand on the shoulder of the one being confirmed.
In the liturgical book “Rite of Christian Initiation of Adults” it is clearly the sponsor who does this:
“Each candidate, with godparent or godparents, goes to the celebrant (or to an associated minister of the sacrament); or if circumstances require, the celebrant (associated ministers) may go to the candidates.
Either or both godparents place the right hand on the shoulder of the candidate and either a godparent or the candidate gives the candidate’s name to the minister of the sacrament.”
(The Rites Volume One, Liturgical Press, 1990, ISBN: 0-8146-6015-0, page 164. RCIA n. 235, in USA edition).
Another mention of the sponsor in the Rite of Confirmation:
“32. Adults who are confirmed, their sponsors, parents, wives and husbands, and catechists may receive communion under both kinds.” (So the sponsor may receive both the Body and Blood of Christ at this Mass.)