This works. You can also copy the code from a gavick demo template:
Demo Template>>Select the required area (small menu icon set)>>Right click>>Inspect element>>Select code>>Right click>>Edit as HTML>>Copy Code>>
Now go to your admin page and paste it in the appropriate position.
For example:
The TinyMCE would have stripped the code and the code reads as
<li data-scroll-reveal="enter bottom over .5s after .25s"><a href="#menu"> <span>Menu</span></a></li>
Paste (insert) the copied code into it:
Copied code: <i class="gk-icon-dinner-set-solid"></i>
Insert it here:
<li data-scroll-reveal="enter bottom over .5s after .25s"><i class="gk-icon-dinner-set-solid"></i><a href="#menu"> <span>Menu</span></a></li>
Save and refresh page.