The font family applied to the design of your document is also controlled by the theme, but you can change the font selections available to you by using the Font tool in the Document Formatting group.
On the Design tab, in the Document Formatting group, click the Fonts arrow.
Scroll through the list to see the font families available for the selected theme. Each font grouping shows the Heading font and the body font.
Choose the font you want to use for your document.
If you want to create your own font combination, click Customize Fonts.
In the Create New Theme Fonts dialog box, click the Heading font arrow and choose the font you want from the displayed list.
Click the Body Font arrow and select the font ...