You need to register with ICAI after 11th grade for appearing CA Foundation exam after you pass 12th grade. 

Post which upon clearance you can appear for CA IPCC exams two groups. 

Upon clearing you need to go for 3year articleship training and IT training of 3months. 

Once you are done with training and articleship you can then appear for CA Final exam and upon clearance of exam you will deemed as CA.