To add a new custom font, open your account settings and go to 'Custom fonts' section.

We support full Google Fonts library. Please consider using Google Fonts first before uploading your own font files.
Choose a font file with .ttf extension and click 'Upload font'. After successful upload, your font will be ready to use.
To use the uploaded font, open template editor, add a text component and pick your font from the font selector on the right side. Your custom font should be available on top of the list.
