Font Awesome displayed as question marks ion macOS I downloaded font-awesome-4.6.3.zip from fontawesome.io. Double click fontawesome-webfont.ttf (under font-awesome-4.6.3/fonts/) to install the font, but I got this,
The preview probably won't show anything because this font doesn't appear to have any normal Latin characters but consists of graphics located in the Private Use Area of Unicode.  See

http://fontawesome.io/cheatsheet/

You should certainly be able to install it.  To use it probably requires the Character Viewer. Others will never see it in your pages unless you set it up as a webfont which gets downloaded automatically when they view your page.