Can we schedule our interview (K1)

I (USC petitioner) got a I-797 form in the mail and an email stating that my fiancé will receive a physical letter in the mail, this email included a case number. She hasn’t gotten that letter yet but after using the case number I received in the email her case states that it’s “ready”. Are we able to schedule a date with our current info or should we wait for whatever physical letter they are going to send?

We’ve gotten everything except the medical exam completed already while waiting.