1. Put font awesome in head_include template
style manager> style name> edit templates>head_include
<link href="//maxcdn.bootstrapcdn.com/font-awesome/4.2.0/css/font-awesome.min.css" rel="stylesheet">

if not working use http
<link href="http://maxcdn.bootstrapcdn.com/font-awesome/4.2.0/css/font-awesome.min.css" rel="stylesheet">

2. Put this in css_additional.css
style manager> style name> edit templates> CSS templates> css_additional.css
/*-- User drop down menu icon --*/
/*-- my profile --*/
#main-navbar .username-container ul.submenu li:first-child a span::before{
font-family: "FontAwesome";
content: "\f007";
padding-right:10px;
}
/*-- post --*/
#main-navbar .username-container ul.submenu li:nth-child(2) a span::before{
font-family: "FontAwesome";
content: "\f086";
padding-right:10px;
}
/*--settings --*/
#main-navbar .username-container ul.submenu li:nth-child(3) a span::before {
font-family: "FontAwesome";
content: "\f013";
padding-right:10px;
}
/*-- logout --*/
#main-navbar .username-container ul.submenu li:last-child a span::before {
font-family: "FontAwesome";
content: "\f08b";
padding-right:10px;
}


/*-- new chat menu icon --*/
#main-navbar .js-pmchat__dropdown ul.submenu li a span::before {
font-family: "FontAwesome";
content: "\f075";
padding-right: 10px;
}
#main-navbar .js-pmchat__dropdown ul.submenu li:last-child a span::before {
font-family: "FontAwesome";
content: "\f061";
padding-right: 10px;
}