If you don't know where to start, the best piece of advice I could give you is to start working out, and seriously. Whether it's at a gym or in your dorm, start and be serious about it. If you can afford to I would say try the gym because even if it may seem scary and everyone's watching you, that's not the case as we all start somewhere, everyone there knows that and they're most likely not even acknowledging you because they're doing their own thing. The reason I'm saying start with this is that, as soon as you start taking this seriously, you'll want to improve in your lifts and physique so much that you'll also start wanting to eat better and sleep more normally, which are going to help you in your overall health and productivity. Another reason is that once this has become part of your routine, you'll have more well structured days, meaning more productive so you can accomplish more. There are so many more reasons but I'll leave you with one more, Confidence. Once you start working out and see even the tiniest improvement you'll immediately start feeling more confident in your own body, which is key to living a healthy life. This confidence will also come from the fact that you know the amount of work you're putting in each day, at the gym trying to better your body, in your dorm or library studying for the course you're doing and how everything is starting to piece together. This will lead to you meeting more people, to people acknowledging you in your house and everywhere you go because of the energy you'll be carrying around with you that people will get attracted to and want to be around.