1)
How does Aharon render the goat a Chatas?
1.
Rashi: By placing the lot on its head and announcing 'la'Hashem Chatas!' 1
2.
Seforno: It is the Goral that makes it a Chatas (and not merely calling it a Chatas). 2
3.
Oznayim la'Torah: The Torah means that Aharon proceeds to perform the Avodah of a Chatas - by sprinkling ite blood (in the prescribed manner) and burning the Emurim.