A few things that may help:
- the theme includes a
svg_iconssetting, if the icon does not appear you may need to add the name here (Discourse doesn’t include every font awesome icon by default, but this setting will add them) - you don’t need to include the prefix for the standard icons, just
user-groupshould work - make sure you’re only looking at free icons (there’s a filter for free on their site), we don’t include pro icons by default because they require a license. Pro icons can be added with a plugin, if you purchase a license: Discourse FontAwesome Pro Plugin