To show the Preview pane, click the View menu and Preview Bar.
As you mouse over selections in the Explorer, the Preview pane displays images. Also, you can preview multiple items if you select a standard from a custom catalog (Projects tab). Note that the standard must have been created within Cap, not Worksheet.
For information on what you can do in the Preview pane, see Preview a product.
Note: Just like the Explorer pane, you can auto-hide and move the Preview pane.