Sacred ministers, those who serve the spiritual needs of others in the person of Christ, in the Catholic Church are ordained by a bishop and by means of a special sacrament called Holy Orders, which creates the hierarchy of deacon, priest and bishop.
This sacrament can be received only once, but a man may also be ordained to a higher order up to the third degree. A man must first be ordained a deacon before being ordained a priest, and he must be ordained a deacon, and then a priest before being ordained a bishop.
Jesus Christ instituted the Sacrament of Holy Orders at the Last Supper simultaneously with His institution of the Sacrament of Holy Eucharist. In order to be able to change bread and wine into the Body and Blood, Soul, and Divinity of Christ, you need priests who have been given this power by virtue of their ordination.
If you are a single, baptized man and wonder if God may be calling you to be His priest; or, if you are a single or married baptized man who would like to know more about becoming a permanent deacon.