After appointing Aaron and his sons to be high priest and priests, it was necessary that they be ordained to those positions. God specified that certain animals along with unleavened bread and oils would be used as burnt offering sacrifices to Him in that rite.
Specific instructions were given regarding the slaughter, preparation and offering of the sacrificial animals. The blood from the second ram sprinkled and placed on various parts of the bodies of Aaron and his sons signified the total dedication of their bodies to the service of God. Seven days of offerings and cleansing were required to complete their consecration.
The priesthood was to be passed from Aaron and his sons to their sons perpetually. However, the succeeding son would be required to be consecrated through the same seven-day rituals.
At the conclusion of the ordination, only Aaron and his sons were permitted to offer burnt offerings for the people. God would meet and dwell with His people in the tabernacle just as Christ dwells with His children today in His church.