I wish to relinquish my rights to my daughter to the mother and her new husband whom wishes to adopt her. How do I go about this?

With an attorney

The mother and step father will file a petition for adoption. In that process their lawyer will provide you with the necessary paperwork. This is not something you can do, it has to be done by the adopting parents.

YOU don't go about this. The step father has to initiate an adoption petititon. Part of the petititon will be a relinquishment of your rights.