John Gill Commentary Leviticus 8:18

"And he presented the ram of the burnt-offering: and Aaron and his sons laid their hands upon the head of the ram." — Leviticus 8:18 (ASV)

And he brought the ram for the burnt offering
One of the two he was ordered to take, (Leviticus 8:2)

and Aaron and his sons laid their hands on the head of the ram ;
as they had done before on the head of the bullock, see (Leviticus 8:14) their right hands, as the Targum of Jonathan, and that at the same time; not first Aaron and then his sons, as a famous grammarian, Aben Ezra makes mention of, thought; but, as he himself says, they laid them on together.