First of all you will have to Link your sub domain at hub pages to Webmaster Tools and to execute the process you have to:
1. Go to: google.com/webmasters/tools/home
2. Click "Add a site – here provide your sub domain URL at HP"
3. Type in your sub domain, e.g., notsosecret.hubpages.com (do not type in www before the sub domain)
4. Click "Continue"
5. The next screen will ask you to verify your ownership. Generally, the first screen to show up under the "Recommended Method" tab will be the correct option but the screen must mention your Google Analytics account. If it does not, click the "Alternate Methods" tab and the Google Analytics bubble and Click "Verify".
6. You will receive the congratulations message for getting your sub domain name verified in Google Webmaster Tools.
7. Now you can verify the feed in Google Feed burner and get the Link or alternatively you can place the widget facility provided by HP.