Here is the "help" direction given to you on your affiliate page/section:
Each program will give you a code to enter below. Click edit (or sign up) for detailed instructions on how to join each program so you can start getting paid.
You are not signing up a second time, but you need to click on it, so you can have access to the spot for your publisher code to be entered. Hope that helps. Otherwise, maybe there is something I'm missing or that you're not telling me. If you need more help, I would suggest that you open a forum thread in the "need help" or "ask for help" section. And, either more experienced hubbers will help you or HubPages Staff might help.