I'm assuming you already have an adsense account.
It's a bit complex so I'll only delve into the basics just so you can place your google affiliate code/publisher ID in websites where you can use it.
1. In new Adsense interface, HOME tab, click the link Account Settings.
2. Right there on top of the Account Information section is the Publisher ID.
3. Place the Publisher ID in the affiliate setting marked Adsense under your profile in HubPages.
4, In order to track yuor income from HubPages, create a URL Channel under Perfromance Report tab.
5. Click the URL channel link found at the top of the left menu bar.
6. At the bottom of the next page, you'll find an "Add URL" button.
7. Place http://hubpages.com there. Or you can specifically place the URL of eahc of your hubs.
If you don't have Adsense yet then you need to create a Gmail account and apply for an AdSense account.
Please don't hesitate to drop me a message for clarifications.