Here a guide for the login.
-Go to

-Log in with your new Nexon ID
-Click Play on the Website
This procedure should open the game and log you in automatically. In some cases it does not happen and a Nexon Game Manager (NGM) Error pops up, this might be due to some firewall restrictions or Anti-Virus Programs.
If turning off those programs does not fix the issue for you, please try as follows:
-Locate the War Rock Launcher in the War Rock Folder
-Double Click it
-When the game opens, click Game Start
-Now you see a Login In Window
-Please enter your Nexon ID and your Nexon ID Password there. (PLEASE DO NOT USE YOUR OLD G1 ACCOUNT TO LOG IN)
Source,

Greetz,
Tyfoon






