As you've probably discovered, during Year 12 friends are often your greatest asset in helping with difficult assignments, discussing problems with study, and in being generally supportive.
University is really no different.
The only problem is that it's unlikely you'll know anyone in your course or in your classes, at least at first. And because uni is a much bigger environment than school, there might be hundreds of people in your course, and thousands of new students in the university, which can be daunting. You'll need to make new friends and establish a new group of people you can rely on, and this may seem difficult when you only see them for two or three hours each week. Keep in mind that nearly every other first-year student is in the same boat and is just as keen to meet new people. So in your first lectures, tutorials and practical sessions, introduce yourself to the people around you - it's well worth getting to know them.