You can apply formatting to all or part of the title text. For example, you can make a single word bold for emphasis. Formatting you apply here is also reflected in the title text on the thumbnail page.
In Page view, display a photo page.
Click the Next button on the views bar until the photo you want to work on appears.
Select all or part of the title text.
Use the options on the Format tab of the Title Properties panel to format the text. See Formatting Text.