How can I go about getting some one to give up his right to his son that he don't won't anything to do with so my husband can adopt him?

You ask him to sign the papers OR you tell him if he allows the child to be adopted he will no longer have to pay child support.

Otherwise there is little you can do.

How do I get him to sign them over

OK how do I get him to sign his right over

You have your lawyer serve him with adoption papers.

You can't MAKE someone sign over their parental rights.

Period.

You can ask, you can inform that he wouldn't have to pay child support after the adoption was complete, or you can beg.

But you can't MAKE him sign away his rights.