You need to login to Google Base (base.google.com) with the login that you requested the multi-client account be created under. This will open your dashboard and you will see a link that says “create another account to manage” Simply register your account(s) like you would in a single user account. Once you have added the appropriate details you will then be taken back to the “My Client Center”. Click the registered display name and register your new data feed. Once you have completed this, upload your feed and allow to process. You can then add more stores in the same way. Checking under each display name will allow you to check the status of each feed.

Please note: Google do ask that you avoid submitting duplicate websites selling similar content as this can lead to disapproval.