Leviticus 9:7
And Moses said unto Aaron, Go unto the altar, and offer thy sin offering, and thy burnt offering, and make an atonement for thyself, and for the people: and offer the offering of the people, and make an atonement for them; as the LORD commanded.
Moses directed Aaron to approach the altar and present his sin offering and his burnt offering to make atonement for himself and for the people, and then to present the offering of the people and make atonement for them, as the Lord had commanded. The required sacrifices were offered by Aaron in obedience to God's command, fulfilling the order to make atonement first for himself and then for the people. This service belonged to the priests' first ministry after their consecration. It was performed exactly as God had commanded.
God accepted the sacrifice and manifested His glory by sending fire to consume the offering upon the altar. At that revelation of divine acceptance and glory, the people responded with praise and worship.