How to hide left navigation on a SharePoint 2013 site.

1] Add script editor web part
2] Past below code in that

<style>

.ms-core-sideNavBox-removeLeftMargin{DISPLAY: none !important}
#contentBox { margin-left: 20px }
</style>


<style>
 .ms-navedit-editLinksText{
  display: none;
 }
 </style>