Thanks for writing in!
Learn to Sass header template is using "Fira Mono" google font. When you import the template, the font will also be created and added in the font manager. You can use it in other elements too. For example if you have a text element, you can simply apply the font since it is already created and added in the fonts manager. Just edit the text element, find the Design > Text tab and change the font family.
Text element settings:
You can use the font in the content or in the footer builder too.
To know more about the font manager, please check this out:
Hope this helps.