If you are upgrading to Microsoft Dynamics GP 2016 from Microsoft Dynamics GP 2013 or 2015, there is no separate update process that needs to be completed for SmartPost 2016.  For SmartPost 2016, you will want to follow the steps in the Installation section on the machine where you want to run SmartPost.  This will install the SmartPost 2016 application into your Microsoft Dynamics GP 2016 installation and the update will be completed automatically in that process.