To view what your Branded Posts will look like to the public you can preview it before approval.
To do this click on the "Branded Posts" section of the Retail Partner Portal, and then scroll to the particular Brand Post you would like to preview in the "Posts Pending Approval" section.
Then click on the "Customize" button underneath of the Brand Post. This will bring up a pop-up window with a preview of what the Brand Post will look like to the public on your page.