In order to upload your product feed to the Google Merchant Center, go to ‘Data Feeds’ in the left side navigation and create a ‘New Data Feed’. Choose the country in which you want your products to display, the googlebase format and enter a catchy name.
Now you can choose to either upload your product feed from the hard drive or create a schedule for a regular automated upload of your product feed from a given URL.
Click back to your dashboard to check the status of your upload. Next to the file you just uploaded you will see a linked status. You can click on that link to get details about the feed validation. If you have any errors, fix them and re-upload your file. Once your feed is validated, it can take up to 24 hours for your products to start appearing in the search results.