Hi Neetu, 

If your basic registration is done, then wait for the final registration which will due from February 21, 2019 to March 12, 2019. During this time, based on the availability, you can select your exam center. It is on first-come-first-serve basis. Once exam center is  chosen, it cannot be changes so please be carefull while selecting the center. Moreover, be prepared and make a wise choice beforehand. Use Careers360 link to prepare yourself. Follow the link given below: https://medicine.careers360.com/articles/aiims-mbbs-exam-centres