God issued the Ten Commandments and additional regulations in Exodus 20-23 as the stipulations of his covenant. He now institutes and ratifies his great covenant with the people of Israel. The Israelites agree to submit to the terms of the covenant. This experience anticipates the reality of the New Covenant established by Jesus Christ.
Moses, as the covenant mediator, sprinkles them with the blood of the offerings. This shows that the LORD had solemnly set them apart as his people. God accepts them based on the atonement that had been paid. But they must now live in accordance with his covenant stipulations.