This is the thing that thou shalt do to them—i.e; "This is the ceremonial that thou shalt use on the occasion." There is a tacit reference to Exodus 28:41, which had announced that the priests were to be consecrated.
Take one young bullock. The offerings were to be provided beforehand, so as to be in readiness when the investiture and anointing were over. Hence they are mentioned first. Rams without blemish. Literally "perfect."
On the offence to God of offering him blemished offerings, see Malachi 1:6-14.