Going to font:/// in Nautilus is obsolte.
You can drag your .ttf-file into .fonts in your home-directory to install that font only for this username:
copy myfont.ttf ~/.fonts
or you can drag it to /usr/share/fonts/truetype to install it for all users:
sudo cp myfont.ttf /usr/share/fonts/truetype
Note: If you have Openoffice opened, it may crash after you installed your font the second way.
You may need to run fc-cache to rebuild the font cache: