Verse 7 transitions from the requirements for the sacrificial offerings to the offering itself. Aaron was instructed by Moses to perform the sin offering and burnt offering sacrifices for himself and the entire congregation. From this point onward Aaron oversees the proceedings; that is, the high priest will officiate over the sacrifices.
7 Then Moses said to Aaron, “Draw near to the altar and offer your sin offering and your burnt offering and make atonement for yourself and for the people, and bring the offering of the people and make atonement for them, as the LORD has commanded.”