You have to have an Adsense, Amazon, Kontera, Ebay or any combination of what I listed. I recommend you sign up for google adsense so that you get paid when people click the ads displayed on your Hubs.
You earn money on Hubpages from the ads displayed in your Hubs, I recommend reading this: http://hubpages.com/faq/#royalties
Remember to read hubs that give advice on the best ways of making money and ask questions in the forums. There are many hubbers here with vast knowledge of earning on this site, just prod us hard enough and we'll give in!