The Sacrament of Baptism is a Sacrament of Healing preformed by an ordained Priest or Priestess of the Levitical Priesthood.

And you must preach unto the world, saying: You must repent and be baptized in the name of Jesus Christ.” –Doctrines of the Saints 12a:59

Those ordained to the office of Priest or Priestess in the Levitical or to the High Priesthood may baptize. They should be dressed in their Garments and Robes of the Priesthood, as instructed in the Law of the Gospel. They should raise their right hands to the square, in the sign of the Law of Sacrifice. They should then follow the instruction on how to baptize as given by Jesus Christ in the Book of Mormon:

Verily I say unto you, that whoso repenteth of his sins through your words, and desireth to be baptized in my name, on this wise shall ye baptize them—Behold, ye shall go down and stand in the water, and in my name shall ye baptize them. And now behold, these are the words which ye shall say, calling them by name, saying:

“Having authority given me of Jesus Christ, I baptize you in the name of the Father, and of the Son, and of the Holy Ghost. Amen. “And then shall ye immerse them in the water, and come forth again out of the water.

“And after this manner shall ye baptize in my name; for behold, verily I say unto you, that the Father, and the Son, and the Holy Ghost are one; and I am in the Father, and the Father in me, and the Father and I are one.” –3 Nephi 5:24-27/11:23-27

Anyone may stand as witnesses to the baptisms, signing the forms of the Fellowship’s records, however a member or ordained Ministry is preferred. They must witness that the words were spoken correctly, and that the individual was fully submerged into the waters. While two are recommended, only one is required. (See also Doctrine of the Saints 2a:62-65.)

It should be noted that baptism is not a requirement of membership in the Fellowship of Christ.

Membership in the Church of Jesus Christ in Christian Fellowship shall be eligible to all who give evidence to their faith in the Lord Jesus Christ and who voluntarily hold to the fundamental doctrines of the Christian faith. When a person chooses to be a part of the Church of Jesus Christ in Christian Fellowship and involve themselves, they are automatically considered a member (Ephesians 4:16).

“A member is one who attends regularly, serves at and contributes financially to the Church of Jesus Christ in Christian Fellowship and can answer the following question in the affirmative:

1. Do you desire to come into the fold of God, and to be called a member of His Fellowship?

2. Have you confessed your sins to the Lord, and repented of them?

3. Are you obedient to the laws of the land?

4. Are you willing to bear another’s burdens, that they may be light?

5. Are you willing to mourn with those that mourn, and comfort those that stand in need of comfort?

6. Are you willing to stand as a witness of God at all times and in all things, and in all places that you may be in, even until death, that you may be redeemed of God, and be numbered with those of the first resurrection, that you may have eternal life?

7. Are you willing to continue in obedience to the Laws of God and Jesus Christ as you understand them?

“Membership, ordinances, callings, and fellowship are open to all, regardless of race, gender orientation, sexual orientation, or marital status.” –Doctrines of the Saints 3c Article V

Also, 

God’s grace, revealed in Jesus Christ, freely moves throughout creation, often beyond human perception, to achieve divine purposes in people’s lives. In harmony with God’s will, the Holy Spirit leads some people already committed to Jesus Christ through Christian baptism to further focus their response through Church membership. Individuals previously baptized of water in an attitude of humility and repentance and as an expression of faith in Jesus Christ may become Church members through the sacrament of confirmation of the Holy Spirit. Confirmation should follow a time of intentional preparation that includes exploring the Church’s mission, beliefs, and understanding of discipleship expressed through covenant with God and others in sacred community. During the confirmation prayer include an acknowledgment of the grace and authority of Jesus Christ through which baptism occurs.” –Doctrines of the Saints 14c:21-25

Baptism should only be performed by those moved to this work by the Holy Spirit of God. Those coming from other Latter Day Saint sects carry their baptisms with them. Likewise, all that feel moved by the Spirit to be baptized may be baptized as many times as they feel moved to do so. All works for the Lord should be done as moved by the Holy Ghost, not to tick a box of a to-do list.