Synposis:
The general format of the command that needs to be executed in an elevated command prompt is:
sc create "InduSoft Web Studio v8.1" binPath=" C:\Program Files (x86)\InduSoft Web Studio v8.1\Bin\StdSvc.exe "
Then you want to edit the service in services.msc and configure it to run under a valid windows user in the LogOn tab.
Finally you need to make a file called WinService.ini and place it in the IWS install directory\Bin folder with the following contents:
[Application]
Configuration=<path to APP file>
Where <path to APP file> is the full path to the project's APP file that you wish for the service to run.
The guide will walk you through these steps with greater detail.