This option is only available for news posts. At this time, the preview while editing content option will not work for any other type of content.
When editing a news post in the workarea, the Preview icon is located just to the right of the Save icon (which you should never use—always Check In or Submit).
Clicking the Preview icon will open a new window to let you see the content as it would appear on the website. This handy feature lets you check your finished product while it’s still open for editing. You can continue to make changes and click
the Preview button again to see them in place (although you will need to close each Preview window before clicking the Preview button again in order for the newest changes to be seen).
When you are satisfied that Preview is what you want to have published, Submit the news post (and close the Preview window).
Note: Brand-new content that has never been checked in nor submitted will not display the Preview icon. This option only becomes available if the content is opened for editing a second time.