After 12th you will be required to give NEET entrance to fulfill your dream.

NEET, conducted by CBSE, is one of the most important medical entrance examinations of India, which provides entry into most of the top medical institutions in the country. The paper tests students on the basic concepts of Physics, Chemistry and Biology.

Rest paper pattern and exam pattern you can check here.

Start with previous year sample papers and then analyse which section you are weak in.
Strategically plan your time: Plan a study routine in advance, allotting time for each subject. This will help to systematically study each subject instead of juggling between many, which is sure to disrupt your concentration and reduce output.

Solve sample question papers on Biology: Sample question papers gives an idea about the topics, the standard expected, and the skills required. Practice and solve problems extensively. Apply conventional methods first, but as the material becomes familiar to you, start applying short-cuts to improve speed.

Practice regularly: Since the applicants are familiar to the syllabus their previous classes. Go through the sample papers carefully and makes notes of the quirks involved. Regular practice will make you more familiar with the subjects and help to quickly interpret and solve problems.

Always make a routine which is realistic and can be pursued, not the one which just remains on the paper.

Hope you get it.
Good luck.