What and how can I perpared myself for college?

It sounds like you've identified your dream school! That is exciting. I recommend you also find 2-3 reach schools (not as difficult to get into as your dream school, but still competitive) and 1-2 safety schools (schools you are very likely to get in) so you aren't putting all your eggs in one basket. Keeping your options open helps in the long run. Your dream school may or may not end up being the school you attend.

Next, find out what your dream school's requirements are: minimum/average GPA, average SATs, preferred level of academic rigor, involvement in extracurricular activities, etc. Then you can work backwards. You can find most of this information on www.collegeboard.org

What you do from here depends on where you are in your college search or application process. If you are a freshman or younger, then you have plenty of time to develop good study habits, enroll in challenging classes (like IB, AP, or honors), achieve high grades, study for your SATs, join clubs and get leadership roles, etc. If you are a sophomore or junior, then you still have some to become a competitive applicant.

Also, it's helpful to have a general idea of what you want to study. For example, if your dream school is UCLA and your dream major is business, then perhaps UCLA isn't the best school for you because UCLA does not offer business as an undergraduate major. Alternatively, you could study a similar discipline, such as economics. Similarly, if you are strongly interested in engineering or science, then going to a school that is known for their English or political science programs but not as strong in civil engineering or chemistry is probably not the best option for you. Of course, college is time to explore and learn, so the major you declare when you apply to college might not end up being the major that you graduate with. Best of luck to your college applications! College is a life-transforming and fun experience regardless of where you go.

From my experience, first we need to have a primary goal and a secondary goal (a back up plan). ex: I love flying, I always wanted to be a pilot due to lack of finance, I couldn't become a pilot but my back up plan was to learn business so I went to college and did BBA and MBA, now I can earn and later learn flying.
So make sure your back up plan is an easier one than your actual plan.
Always aim for 2 targets, so that in case the first one fails the second one is always there to back up