1. Include the defs.

   <div style="display; none"> {{ SVG CONTENTS HERE }} </div>
   

2. Make an xlink ref.

   <svg class="icon icon-phone">
           <use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-phone"></use>
   </svg>
   

3. Add some stylez.

   .icon {
       display: inline-block;
       width: 1em;
       height: 1em;
       stroke-width: 0;
       stroke: currentColor;
       fill: currentColor;
   }     
   

Cheers to Icomoon and Font Awesome.