Add repository via .deb-file

curl -sLO https://repo.nordvpn.com/deb/nordvpn/debian/pool/main/nordvpn-release_1.0.0_all.deb && dpkg -i nordvpn-release_1.0.0_all.deb

or

add-apt-repository "deb https://repo.nordvpn.com/deb/nordvpn/debian stable main"

Install via apt

apt-get install nordvpn

show settings

nordvpn settings

enable/disable setting

nordvpn set <SETTING>

Use this script to log yourself in automatically without typing your credentials
You need the software “expect” for this to work, install via “apt-get install expect”

#!/usr/bin/expect -f

set force_conservative 0  ;# set to 1 to force conservative mode even if
                          ;# script wasn't run conservatively originally
if {$force_conservative} {
        set send_slow {1 .1}
        proc send {ignore arg} {
                sleep .1
                exp_send -s -- $arg
        }
}

set timeout -1
spawn nordvpn login
match_max 100000
expect -exact "\r-\r  \r[32mPlease enter your login details.\r
[0mEmail / Username: "
send -- "YOURLOGINNAME"
expect -exact "YOURLOGINNAME"
send -- "\r"
expect -exact "\r
Password: "
send -- "YOURPASSWORD\r"
expect eof