First off, congratulations on getting accepted into a 4-year. That's a major accomplishment and you should be proud of making the most of the opportunities at your 2-year college.
So how to prepare for the transition... I'd suggest that you keep doing the things that have helped you to be successful at your 2-year college. A 4-year university won't necessarily be more academically challenging than what you're used to. Even if you do find your new school more difficult, it sounds like you haven't really been challenged academically so far. So I wouldn't worry too much.
The main thing that will help you to be successful is to consistently show-up and pay attention in class. Engage with the professors and teaching assistants. Ask questions and make the most out of your time while you're in class. Often your teachers will tell you exactly what you need to do to get good grades on papers, projects and exams.
Also, procrastination is a killer. Don't leave everything to the last minute. Make sure to keep up with everything on a week-to-week basis.
Last thing is to make the most out of the full university experience. Go to the sporting events. Be socially active. Join clubs, etc. Make as many friends as you can. There's more to life than just studying and grades. Your time at university can be some of the best years of your life and lead to life long friendships.
Good luck! I'm sure you'll do great!