I am adopting my brother's daughter and for this purpose I did all the research and I have gone through all the legelaities. I can say I have read through entire JJ Act 2015.
Your case is related to In-Country Relative Adoption as per CARA (Central Adoption Resource Authority). You need to register on Carings portal of CARA (cara website link) and gather all the documents as per schedule VI of regulation 2017 of JJ Act 2015.
I did followed this process as specified by CARA and my application is in progress. In my case all the documents are ready and submitted to CARA. Now I am just waiting for CARA to approve my documents so that I can apply for court order. Once court order is issued, CARA will direct concerned authorities to issue birth certificate of the child having our names as parents and accordingly her passport will be issued.
I must say that eligibility and procedure is clearly mentioned on CARA website. I will be available on 9886962410 for any in-person talks on this matter.
Hope it will be useful to you!