This Mass, which the bishop concelebrates with his college of presbyters and at which he consecrates the holy chrism and blesses the other oils, manifests the communion of the presbyters with their bishop.
The holy chrism consecrated by the bishop is used to anoint the newly baptized, to seal the candidates for confirmation, and to anoint the hands of presbyters and the heads of bishops at their ordination, as well as rites of anointing pertaining to the dedication of churches and altars. The oil of catechumens is used in the preparation of the catechumens for their baptism. The oil of the sick is used to bring comfort and support to the sick in their infirmity.
Presbyters are brought together and concelebrate this Mass as witnesses and cooperators with their bishop in the consecration of the chrism because they share in the sacred office of the bishop in building up, sanctifying, and ruling the people of God. This Mass is therefore a clear expression of the unity of the priesthood and sacrifice of Christ, which continue to be present in the Church.
:: Ceremonial of Bishops, no. 274
The Roman Missal, Third Edition, states that "The reception of the Holy Oils may take place in individual parishes either before the celebration of the Evening Mass of the Lord's Supper or at another time that seems more appropriate." (Chrism Mass, no. 15)
While no model for this reception has been published in any ritual text, the USCCB has provided a simple Order for the Reception of the Holy Oils which was confirmed for use by the Holy See in 1989.