Hello Aspirant,


First of all you will have to take science as a subject for class 11 and 12 that must include PCM.After that you can join a good coaching centre for preparation of jee mains and advance.You have to keep in mind that you must also take care of your HSC studies as well as the competition level.Always be honest with yourself.Study hard without distraction and disconnect from social media.
Have a study plan and follow it everyday.
Always practice the past year questions and samples.
Its just simple study hard and you defenetly will crack jee and get into IITs.

I hope this helps.