Go to my account, then click earnings. click google adsense. Here whether you can apply for an adsense account if you don't have one or you can integrate the existing account. Click I already have an account. You will need to submit your publisher Id, post box number and the last 5 digit of your cell phone. Then go to your email (adsense account email) check the inbox and verify the request by clicking the link. Then in the hubpages earning section you can see google adsense is active.