hey sri 

your question is quite incomplete . please make it clear and resend with necesarry details onwhat you want to ask .however if you want to pursue mbbs form aiims ,then you have to be very clear to its elibility criterias and procedures .aiims is the best institute inindia thus the competetion remains very high .kindly go through eligibility criteria .you will also get to know about needs of your class 12 marks 

https://medicine.careers360.com/articles/aiims-mbbs-eligibility-criteria

best wishes