You have the ability to add a default font at the system level or can update each Font at the template level. To add a custom Font that is not on the selected list
Navigate to the Admin > More and select Fonts
Tick the Plus Icon to create a new Font
Add relevant information and Save
The new Font will now appear in the Base and Heading Font drop down list
Points to Note:
If you choose "Custom" in the type dropdown list, please contact the support by email support@communic8.com. We will need the file or the location of where it's hosted and we will add the font to your instance.