English Standard Version
Leviticus 16:23 Then Aaron shall come into the tent of meeting and shall take off the linen garments that he put on when he went into the Holy Place and shall leave them there. 24 And he shall bathe his body in water in a holy place and put on his garments and come out and offer his burnt offering and the burnt offering of the people and make atonement for himself and for the people.
It seems that Aaron bathed inside the tent of meeting.