That’s part of the onboarding experience. I believe once you officially commit, you have to create your first IU computing account which can be found through One.IU. You will have to have a student ID so you have to be assigned one and be in the IU system to be assigned a student ID.
Financial aid stuff will come your way more in the spring semester. If you know you’re going to IUSM for sure (even if you haven’t been accepted), I’d submit your FAFSA to IUPUI. I did that last year and that helped fast track financial aid information for me as a first year.