the answer to this question will depend on where the child is residing. If the child is in Texas, than you should ask your question in the TX forum. If the child is in OK or has lived in OK recently, I would recommend consult with a family law attorney in Lawton. terminating parental rights is a very tricky area as courts tend to favor relationships with the natural parents. However, it is possible to terminate the parental rights of a natural parent. Almost all family law attorneys offer a free consultation and a local Lawton attorney will be familiar with the local court system. Schedule an appt with them soon if the child has recently lived in OK but has moved.
The only attorney I know in Lawton is James Willson. I am not sure if he does family law but can direct you to someone that does and is competent or ask your friends that have had divorces who they used and whether they were happy with them.
If this is a Texas matter, a petition to terminate needs to be filed in the Court of continuing jurisdiction or, if none, a district court in the county where the child resides, and you would execute an affidavit voluntarily terminating your parental rights. There are a number of issues, including the realities involved in losing all rights to your child and whether or not a judge will grant the termination without a new adoptive parent, which you didn't mention. For these reasons and more, you should definitely discuss this with a good family lawyer before doing anything.