There are two ways to preview content. 

While editing a piece of content, you can preview content by clicking the Preview button in the top right-hand corner of the page. The preview will open in a new tab or window (depending on your browser settings). 

A GIF shows how a user previews content while in a content type in TerminalFour.

You can preview content from within a section as well. Click the piece of content's Actions button Actions button and select Preview. The preview will open in a new tab or window (depending on your browser settings). 

A GIF shows how a content moderator previews a piece of content from within a section.

Learn how to preview a section from the site structure.