To use the Font Awesome icon picker, change the value of the fred.icon_editor system setting in the Fred namespace to FAEditor.
We've added a system setting to link to FA on your frontend so that you are always using the same version as this plugin. You can add the link like so:
<link href="[[++fredfaeditor.link]]" rel="stylesheet" type="text/css">
This link will be updated whenever you update the FA Editor.