If your site is using a third party catalog such as the WHI OE or Aftermarket catalog, the current method to create feed is accomplished in a few steps:
1) Add the page mainteditgooglebase.wws to your URL, for example: http://www.site.com/mainteditgooglebase.wws
2) Click the download button
3) The system will create a file that can then be uploaded to Google. Keep in mind that since you use a third party catalog that is delivered via a 'web service', you are not able to export the catalog as you do not have the catalog stored at your site. Your inventory feed will only contain those items ever looked up at your site. For more information about how your site works, click here.