Provided there is one Catholic sponsor, a baptized non-Catholic Christian may serve as a Christian witness for Baptism only. This person is a Christian witness and not a sponsor. They must be at least sixteen years old, a validly baptized Christian living an upright life, cannot be either parent and cannot be a Catholic who has left the Church. A Christian witness may never be a non-baptized person. For example, Jewish or Muslim godparents are not permitted by universal church law. The notation "Christian witness" is placed under the name of the non-Catholic Christian witness in the baptismal register.
If you are a St. Patrick's Parishioner, please see Fr. Rob or Fr. Marius at the end of Sunday Mass and request a sponsor form or present the form you have with you (the form the baptism couple has given you). The priests will bring you to the Sacristy of the Church where they will sign the form and affix the church seal.