YOU NEED TO GET AN ATTORNEY TO ASSIST YOU WITH THIS. I can only give you a general idea concerning termination of parental rights here; it's not a simple matter. The most important thing to remember is the courts will always consider the best interests of the child as a paramount issue.
Any termination of parental rights in Wisconsin will require a hearing, but by far the easiest path would be for Dad to voluntarily terminate his parental rights. I don't know from your question whether that is an option, but for some people in this situation where there is no relationship per se with the child, the opportunity to terminate the rights - and obligations - that go with parenthood can be attractive. Just so you know, once parental rights are terminated you have no recourse to get child support from Dad - this terminates both rights and responsiblities.
If Dad isn't willing to do this voluntarily, you will need to file a petition for termination of parental rights. The law requires proof that includes a laundry list of things that establish the grounds for termination. These include abandonment, parent failing to communicate with or visit child for extended periods of time, child abuse, failure of the parent to assume parental responsiblity, etc. This is not a complete list.
There is normally a guardian ad litem appointed to represent the best interests of the child. The GAL represents the child, not either of the parents.
Terminating someone's parental rights is considered a weighty matter and the courts will not do so lightly, nor without you having established proof on one or more of the statutory grounds for termination. Please consult an attorney for this, and good luck!