Mint Linux Installing Fonts System-Wide

check which fonts are already installed

fc-list

Navigate to /usr/share/fonts

cd /usr/share/fonts

place your downloaded *.otf and *.tff fonts in this directory.

To make the system aware of the new fonts, update the font cache by running the following command:

fc-cache -f -v

As a side note, specific users can have fonts in their home that are not available system wide. They simply place them in ~/.fonts and run 'fc-cache -f -v' as a regular user.