The support forum for NZBGetVPN is located here.
This application does not have any specific setup instructions documented. If you need assistance setting up this application please visit our support page.
NZBGetVPN WebUI Access
If you're attempting to get access to the NZBGetVPN WebUI remotely outside of your home network, you are going to have to do this through a reverse proxy using SWAG. Full details and steps are outlined here VPN Information.