Open ACP, go to Global CSS and add
.mainMenu .boxMenu > li > a::before {
font-family: FontAwesome;
margin-right: 7px;
}
Now, get the content
value of Font Awesome 4 icon that you want to use. Click here if you don’t know what to do.
And add it to global css:
.mainMenu .boxMenu > li > a[href*="forum"]::before {
content: "\f0e6";
}
.mainMenu .boxMenu > li > a[href*="members-list"]::before {
content: "\f0c0";
}
Effect?