Hi! First of all - congrats! Your first semester of college is a super exciting time.
I guess the main thing I want to say here is don't feel scared or nervous. I know it's hard not to - I went from a graduating class of barely 100 students to attending a university of more than 50,000. I know it can be overwhelming, but just remember that there are tons of other freshmen in the exact same situation as you. You're not the only one who has no idea what they're doing, so take advantage of this and make some freshmen friends to make things a little easier on you. That way, you have someone to endure these "firsts" with. Furthermore, it pays off to make friends that are older than you, as well. They know the ropes and it's good to have upperclassmen friends that will be a little more honest with you than say, advisers or other college/university staff that are paid to tell you only certain things (and maybe withhold some of the grisly details).
Secondly, STUDY. I never had good study habits in high school so the first semester of my freshman year was a difficult adjustment for me! Make sure to set aside more than enough time to study. It's not healthy to stress because you know you could be doing better. Sometimes it's okay to pass up social events to get some work done. Then, you have more time to chill and you're stress-free knowing that you're all caught up. However, I guess I might be contradicting myself by saying this, but leave some time for fun, too. Of course focus on doing a good job in school, but when you can afford to take a break, take one. It's not healthy to be constantly working 24/7. You'll exhaust yourself and you'll get cranky and your friends won't want to be around you (trust me, I know from experience). Find a healthy balance between having a social life and studying, and college will be a breeze.
Lastly, I'll leave you with a little bit of wisdom that my uncle shared with me the summer before my freshman year of college: "College is the most amount of freedom you'll ever have with the least amount of responsibility." It sounds obvious, but it's so true. Take advantage of being away from home. Stay out late if you want, but don't sacrifice your grades for it. Be responsible, but realize your parents are still there to help you out. Have fun, make friends, and learn (that's what you're there to do, of course). Figure yourself out. Find out who you are and what you want to do for the rest of your life. This is the last chance you have to really * up and change your mind 100 times before repercussions get really intense. So don't feel bad if you want to change your major 4 times - try out new things, see what you like.
Hope your freshman year goes great! And know that we're all here throughout the year if you ever need more advice.