Hi,

To customize this, you can go to the file app\design\frontend\sns_nazic\default\template\sns\blocks\mainmenu.phtml, modify the class of the codes below (remove visible-md, hidden-md):
<div id="sns_custommenu" class="visible-md visible-lg">
<div id="sns_mommenu" class="menu-offcanvas hidden-md hidden-lg">

Thanks,