I second dpkn.
There is no need to panic. There is a learning curve to acquire the knowledge of any kind.
As far as the preparation is concerned, along with the basic fluid mechanics and computational methods you are learning through the books, get accustomed with some basic mathematical operations like scalar and vector mathematics, matrix operations, calculus etc. ( Assuming that you have not studied these in your high school or BSc. If you have, brush up the basics, and start learning a bit about differential equations ) These will once again be covered in the course at the University, but, it is good to have an understanding of them beforehand.
You have time untill September - October before you really get into the grove of beginning the actual course.
Lastly, follow the lectures closely, do the assignments on your own. There are a ton of help available - all you need is to just ask. The professors are super helpful, and if you show that you are doing your part putting in the effort, they will hep you out to reach your goal.