en_tn/lev/16/18.md

He must go out to the altar that is before Yahweh

This is the altar of sacrifice just inside the courtyard of the tabernacle.

make atonement for it

Like the holy place and tent of meeting, the altar is unclean because of the sins of the people.

horns of the altar

"the projections at the corners of the altar." This refers to the corners of the altar. They are shaped like the horns of an ox. See how you translated this in Leviticus 4:7.