You can do this in the Typography settings of your site.
Please go to X > Theme Options > Typography.
If the Font Manager is disabled:
when you go to X > Theme Options > Typography > Body and Content > Body Font and Heading Font you will have a selection of fonts you can use which are google fonts and system fonts.
If the Font Manager is enabled, you will have to add first the font you want to use using the Font Manager so you can set them to the body and heading font settings of the Theme Options.
Hope this helps.