After your AdSense account is activated, then next step is to approve HubPages.com, Log into your AdSense account, go to the screen that shows your website url's. You will see it says 'pending' for HubPages. Next to that you will see a link that says "grant access" - click on that and you should be good to go.
I wrote a detailed Hub "Step-By-Step Picture Guide to Successful AdSense Activation" to help with that. You can find the link to it on my profile page under "Help For Other Hubbers".