Hi, how can I add email and telephone icons to the Header Top Bar?

I tried with <i class="fas fa-envelope"></i> but its messing the code.

You can add custom CSS, something like this:

.top_bar_phone:before {
     font-family: FontAwesome;
   display: inline-block;
   padding-right: 6px;
   vertical-align: middle;
  content: "\f095";  
}

.top_bar_email:before {
     font-family: FontAwesome;
   display: inline-block;
   padding-right: 6px;
   vertical-align: middle;
  content: "\f003";  
}

Worked like a charm, thanks @Brian and team.