The Hik-Connect App solution does not require you to set up any port forwarding.
To use Hik-Connect, your NVR must be able to 'phone home' to the Hik-Connect web portal.
To do this, your NVR needs to be connected to your home network.
The 'Network Settings' in your NVR's Configuration need to be correct for your network and router.
i.e.
It needs to have an IP address within your router/network's domain range.
It needs to know your router's IP address (they probably refer to it as your gateway)
It needs to have valid DNS entries entered (most people use Google's Primary & Secondary DNS addresses: