From what I hear, your MOC and occasionally your BGO should contact you about your appointment right before you receive an email regarding a status change and portal status change. Then a week or two later, you should get the BFE. But everyone is different. I've done some reading around on the forum and this is how most people say they were notified. Just to be clear, the BGO doesn't offer the appointment, he notifies you; the only one who can make an appointment offer is the admissions board itself.
Once an offer of appointment has been determined by the board they will give the MOC about one week to call you. After that time period your portal will be updated. If you portal gets updated you will receive an email that the portal has been updated. Your BGO is not supposed to notify you.
Well, my nomination source let me know beforehand about my appointment and I informed my BGO about my appointment. I just wasn't sure because I know assemblies have been held before to give an appointment in person.