Add note about rebooting

nordvpn-bin.install

@@ -1,8 +1,10 @@
 post_install() {
   echo ':: In order to enable nordvpn you have to start the following service:'
   echo '     sudo systemctl enable --now nordvpnd'
-  echo ':: You have to add yourself to the nordvpn group to use it:'
+  echo ':: You have to add yourself to the nordvpn group:'
   echo "     gpasswd -a USERNAME nordvpn"
+  echo ':: You then have to restart for the group to be created:'
+  echo "     reboot"
 }
 
 pre_install() {