In order to use Font Awesome make sure to include the "Font Awesome" symbol on the page.
Knockout uses the Font Awesome 5 Free icon system, implemented as a font. This means that any unicode glyph from the free font can be pasted as text, provided it's given a class corresponding to its set. Solid and Brands sets are supported. These classes can be combined with other classes for additional styling.
Icons can also be added as pseudo-elements in custom code using unicode or the unicode glyph.
The icon cheat sheet can be found here. To update Font Awesome to the latest or to upgrade to Font Awesome Pro, visit FontAwesome.com.
To upgrade to FontAwesome 6, uncomment the FontAwesome 6 code in the Font Awesome embed within the Custom Code symbol & delete the FontAwesome 5 code. You can found Font Awesome V6 icons here.