In many states, you can go to the county courthouse and pick up documents to file on your own. Without knowing all of the facts of your case, I can't be as helpful as I'd like to. But, I can tell you that (at least in Oregon), it's fairly easy to get the paperwork done without an attorney, especially if the other party is in prison.
If you have never filed for custody of the child, you would want to just file the paperwork to get custody. You'll have to get the father served in prison, but that shouldn't be too hard. Prisons are usually happy to help complete service for people in situations like yours.
As for terminating his rights, that is a much bigger issue and you will need the help of an attorney for that one, if you can do it at all. Usually it involves getting someone else to adopt the child or child welfare to step in. A lot of the time it's not something that can be done even with an attorney's help.