Best way is to find the home station of teams in the finals. I don't think there is one that does all, maybe I'm wrong. Would need to stream it though.
There is an option to use one of the NBC Sport apps to stream the finals- I think you do need to have an account with one of the many cable companies- DirecTv, Dish Network, ATT, Xfinity, Mediacom.
Your best bet is to find a hometown station for one of the teams playing at that time. I believe the IHSAA charges $200/game for radio broadcast rights to each station that wants to do it so not many do it unless it is a hometown team.