@Valeriy, what I actually do is to add the two interfaces before the installation of Nethserver. The I install everything until I would be able to login via Webinterface.
Now it depends if you have both adapters in the same network or in different networks. I assume you will have it in different networks.
So basically if you have Adapter 1 in Network A and Adapter 2 in Network B and your PC is in Network A, try to reach the configured IP Address of your Nethserver (https://ip-address:980). When you cannot reach it, try to switch the Networks in your Hyper-V config: Adapter 1 with Network B and Adapter 2 with Network A. Now you should be able to reach your Nethserver.
If you have another problem, please tell us more about your situation, your network and the configuration you want to have.