What does Leviticus 9:7 mean?

Then Moses told Aaron, 'Come to the altar and offer your sin offering and your burnt offering to make things right for yourself and for the people. Then offer the people’s sacrifices to make things right for them, just as the Lord commanded.' Leviticus 9:7 - Modern Text Bible

(Aaron is to act as a mediator, first dealing with his own sin, then helping the people get right with God.)