To publish a draft: put it online or offline, you must go to the product configuration page: from the list of your products, click on the image of a product or use the action selector of the product in question and click "Edit"
Enter the information about your product, select the status you want and click "Publish"
(Note: in order to publish your first product, you must have entered your billing information)
To change the status of a published product, you can use the status selector located in the product list
Open the selector then click the option you want: Online or Offline to change the status of the product instantly.