Assuming you have openvpn, fish, fzf, and fd installed
Grab the NordVPN openvpn config files and unzip them
curl -Lo ~/NordVPN/ovpn.zip --create-dirs https://downloads.nordcdn.com/configs/archives/servers/ovpn.zip
unzip ~/NordVPN/ovpn.zip
Grab the function defined in the file below
curl -Lo ~/.config/fish/functions/nordvpn.fish --create-dirs https://gist.githubusercontent.com/oscarduignan/1e0fafb88d8d8c69162d831937cc2e50/raw/nordvpn.fish
Before you can run the function you need to add your nordvpn username and password on separate lines to ~/.nordvpn
Once that is done you can now run nordvpn
and you'll see a list of the openvpn configs to choose from in fzf, when you choose one it will load that connect using that config with openvpn (animated gif in comments)
I haven't tested the installation steps above but they are a condensed version of what I did to get it working for myself locally