Check out the documentation about adding fonts: https://docs.mendix.com/howto/front-end/customize-styling-new/#local-fonts
Hope this helps you get started!
Instead of downloading the font files you can directly use the CDN apis from the google itself.
I have been adding an example for you
Navigate to the above link there you can see the below api
copy this API and paste the CDN API in the place of $font-family-import
and change the $font-family-base to its font family name and run your application.
you can able to see the changes in the font of the application as I have been added below Sceenshot.