I applied through my college career website. The on-campus interview was fairly easy-- they mainly just asked behavioral questions, some fashion trends I was into, and different brands I liked. I was asked when I was had to be a leader because being a brand ambassador is all about being a fashion leader and getting people on campus to go to the store. The interviewers were very bubbly. They emailed all the ambassadors a week or so later.
We discussed the pay -- they didn't pay, but we did have $50 gift card incentives for turning in email addresses.