Once you’ve successfully tested your feed you will probably want to set up your Merchant Centre account to automatically fetch your feed periodically.
Log into your merchant centre, and head to Data Feeds. Against your active feed, choose the Create Schedule option. You’ll be asked how frequently you want Google to pull your feed, and the URL to your feed. You can find this on the settings page (Downloads » Settings » Product Feeds)
Once you’ve entered this information, choose Schedule and Fetch now. Google will check that they can download your file and automatic refreshes will be scheduled according to the frequency you selected.