@Watang, first you will probably receive confirmation from the main university that you were accepted (as you filled out an online application to the University), as that needs to happen in order for your supplemental application to go forward. Once that has happened (don’t worry, the standards aren’t really too high there, trust me), after that you will receive confirmation of whether or not you got a BA/MD invite to interview from the medical school.
I would print out confirmation for your records from the online supplemental application that it’s been submitted. I would also confirm receipt of your high school transcript, ACT/SAT score report, and reference forms, as well by UMKC. You can either nicely and politely email or phone call confirming that they have everything there to complete your file.