Procedure to adopt a child

I think you are a Hindu.  The adoptive child shall be below the age of 15 years. The natural parents and adoptive parents shall perform the rites/homa, etc., as per the custom prevailing, and execute the adoption deed, which may be registered.

A retired pensioner can adopt a child by registering on the CARA website, completing the online application with required documents like proof of identity, income proof (pension statement), and a medical fitness certificate, and then completing a home study, court approval process, and post-adoption formalities with the help of an adoption agency.

The maximum age for a single parent is 55, and the composite age for a couple is 110 for children up to 18 years old. 

Pensioner is muslim and she wants to adopt her sister child the age of girl is 7years 

Muslim law does not recognize formal adoption in the way the Hindu Adoption and Maintenance Act (HAMA), 1956 does.

A Muslim can take a child under “kafala” or guardianship, but the child does not acquire inheritance rights in the adopter’s property automatically.

The child’s biological parents remain the legal parents in law.

So, under Muslim personal law, she cannot legally “adopt” in the full sense (i.e., creating parent–child status for all legal purposes).

Under the Juvenile Justice (Care and Protection of Children) Act, 2015 (JJ Act)

This Act allows any Indian citizen — irrespective of religion — to legally adopt, provided the adoption is done through the Central Adoption Resource Authority (CARA) under the JJ Act.

It is better to seek professional services of a local prudent lawyer for proper analyses of facts, guidance and necessary adoption proceeding, if permissible in law. 

Take help of local lawyer. 

Presently, it is the settled law that, in matters of adoption, provisions of JJ Act overides the dicates of Muslim Personal Law.