USC Other Recommenders Help

Hi,
I’m applying to USC through the common app and I saw that they didn’t have a choice for other recommenders. I saw previously on CC that other students managed to turn in other recommendation letters besides just teachers and counselors.
How would you do this?
I already emailed USC, but they didn’t give me a direct answer and said I would need my USC ID, which would only be provided if I got accepted (which defeats the purpose of sending in another recommendation letter).

Any help?