WOW! It’s really amazing to see such a question. Let me clap for you first, because deciding to prepare for competitions at such a time is a brave decision. But, if you are really determined to prepare from now, and if you will take this really seriously, i can assure you a very good rank and be ready for interviews!

Now, let’s see what you need to do-

1. Focus on Science and Maths- Please please don’t ever think that you are going to take biology, so maths is not important, just don’t do that! Take you maths and science very seriously this year, because, Science of 10th class will going to create a base for further details in 11th and 12th and maths of 10th class will going to serve you a lot in Physics, trust me here!
2. You are 10th passed- Congrats!, now, tighten your seat-belt for upcoming detailed version of everything! Now, how to go further, that i have already written an answer on that, please check out- HERE.