You can take any fonts installed in your website/theme and import them into Shogun's editor.
Basically the way it works is that your site's theme styles need to load in whatever fonts you want to use. You can add fonts into your theme, or use something like Google Fonts (https://fonts.google.com/).
Guides on adding fonts to themes
How to add your font to Shogun
Once the fonts are in your theme, you can add the names of them into the settings section inside Shogun.
Settings > Fonts (at the bottom) > Add the Font name
The font name is case sensitive, spelling sensitive, and syntax sensitive. Some fonts will have single quotations around them (i.e. 'font name').
Once a Custom Font has been added to your Shogun settings, it will appear as an option in the Text element's font menu.
My font is not showing
Check the integration with your theme, the font will need to be integrated with the main CSS of your theme using the
@font-face selector. If you are having trouble with this, we would recommend getting into contact with the developer of your theme, or with Shopify support directly.