IconMoon Guide

use data-icon attributes

      <h2 id="stats">

      <span aria-hidden="true" data-icon="&#x21dd;"></span>
        Stats
      </h2>

use css

<a href="#" class="btn btn-small" iclass="ico-plus-circle">
  <i class="ico-plus-circle"></i>
  <span>  Add project</span>
</a>

bootstrap adjust hack

.btn-large [class^="ico-"],
.btn-large [class*=" ico-"] {
  margin-top: 2px;
}

.btn-small [class^="ico-"],
.btn-small [class*=" ico-"] {
  margin-top: 0;
}

.btn-mini [class^="ico-"],
.btn-mini [class*=" ico-"] {
  margin-top: 0px;
}

[class^="ico-"], [class*=" ico-"] {
  display: inline-block;
  width: 16px;
  height: 16px;
  line-height: 16px;
  vertical-align: text-top;
  
  margin-top: 1px;
}