After your 12th, I suggest you to complete your graduation first as this is the basic education you should get. You can do short term, certificate courses, graduation courses in arts and drama. Get some experience in theater side by side. You can build your acting skills with small competitions in college and add it later to your experience. You can also try modelling initially to get a boost in your career.

You should have good memorization, communication skill and passion in acting. You can start participating in school, college events, participate in dramas, acting at state-national level and this is how you can start buiding your portfolio.

This is how you can start and take a direction towards your aim.

Good Luck!!