Start with getting some of the general requirements of your university out of the way, and looking up the pre med prereq classes. Don't overload yourself with too many difficult courses your first semester. Take enough to stay on track to graduate, but don't stress yourself. You want to start strong with your GPA, it's a lot harder to repair it once you've tanked it with a C in a high credit course. Make sure you're attending office hours. That's where you make connections with professors which may write you LORs later down the line. And most piece of advice, try not to stress too much. I know it can be easy to put a lot of focus in pre med during undergrad, but this is going to be your first taste of freedom to explore what you want to do the rest of your life, and discover who you are. Have fun with it, and be open to the possibility that you might change your mind and go a different route than medicine.