05-07-2018 06:23 AM
The Geospatial Portal does not come with such a functionality built in, and instead relies on the capabilities of its hosting in IIS as ASP.NET. As you already noticed, there is some description of how to use that in the documentation you linked. It is assumed that additional knowledge can be obtained from IIS/ASP.NET related resources.
It's a shame that this didn't work out for you, but without you saying what exact problems you have while setting up an authorized WebMap Publisher site, it will be very hard to come up with any hints.