In order to join the Indian armed forces as a doctor you must have studies in armed forces medical college and also you have to clear the neet to get admission into afmc. The medical fitness shuold be according to the criteria by ministry of defence. And here you have cleared your MBBS then but it might be from AFMC so you can apply in armed forces for the post of doctor. You will be subjected to the interview round also conducted at delhi. You will have to keep yourself updated witht the advertisement of the armed forces doctor. In the advertisement you will find all other necessary details and qualification required. The advertisement publishes during the month of February and August. Also you can read the more about the same at the link given below.

https://www.careers360.com/question-how-to-join-army-after-doing-mbbs